Endothermic reaction of a feed gas heated by resistance heating

ABSTRACT

Structured catalyst arranged for catalyzing an endothermic reaction of a feed gas, said structured catalyst comprising a macroscopic structure of electrically conductive material, said macroscopic structure supporting a ceramic coating, wherein said ceramic coating supports a catalytically active material, wherein the electrically conductive material at least partly is a composite in the form of a homogenous mixture of an electrically conductive metallic material and a ceramic material, wherein the macroscopic structure at least partly is composed of two or more materials with different resistivities.

FIELD OF THE INVENTION

The invention relates to a structured catalyst for carrying out anendothermic reaction of a feed gas, wherein said structured catalystcomprises a macroscopic structure of first electrically conductivematerial, said macroscopic structure supporting a ceramic coating,wherein said ceramic coating supports a catalytically active material.

BACKGROUND

Endothermic reactions will often be challenged by how efficient heat canbe transferred to the reactive zone of the catalyst bed within a reactorunit. Conventional heat transfer by convection, conduction, and/orradiation heating can be slow and will often meet large resistance inmany configurations. This challenge can be illustrated with the tubularreformer in a steam reforming plant, which practically can be consideredas a large heat exchanger with heat transfer as the rate limiting step.The temperature at the innermost part of the tubes of the tubularreformer is somewhat lower than the temperature outside the tubes due tothe heat transfer rate through the walls of the tube and to the catalystwithin the tubes as well as due to the endothermic nature of the steamreforming reaction.

One way to supply heat within catalyst instead of outside the tubeshousing the catalyst is by means of electrical resistance heating.DE102013226126 describes a process for allothermal methane reformingwith physical energy reclamation, wherein methane is reformed by meansof carbon dioxide to synthesis gas consisting of carbon monoxide andhydrogen. The starting gases CH₄ and CO₂ are conducted in a fixed bedreactor consisting of electrically conductive and catalytic particles,which is electrically heated to temperatures of about 1000 K. Theconversion of the reactant gases and the generation of heat of thegenerated synthesis gas take place in the fixed bed reactor.

It is an object of the invention to provide an alternative configurationof an electrically heated structured catalyst and reactor system forcarrying out endothermic reactions of a feed gas.

It is also an object of the invention to provide a structured catalystand reactor system with integrated heat supply and catalysts.

It is a further object of the invention to provide a structured catalystand a reactor system for carrying out endothermic reactions of a feedgas comprising hydrocarbons wherein the overall energy consumption isreduced compared to a system with an externally heated reactor, such asa side fired or top fired steam methane reformer (SMR), which is thereference for industrial scale steam reforming. By utilizing electricheating, the high temperature flue gas of the fired SMR is avoided andless energy is therefore needed in the reforming section of theelectrically heated reactor.

It is another object of the invention to provide a structured catalystand reactor system for carrying out endothermic reactions of a feed gas,e.g. a feed gas comprising hydrocarbons, wherein the amount of catalystand the size of the reactor system is reduced compared to conventionalreactors for carrying out endothermic reactions. Moreover, the inventionprovides for the possibility of tailoring and thus reducing the amountof catalytically active material, while having a controlled reactionfront of the reaction.

It is furthermore an object of the invention to provide a process forproduction of a product gas from an endothermic reaction of a feed gas,e.g. a feed gas comprising hydrocarbons, wherein the product gas outputfrom the reactor system has a relatively high temperature and arelatively high pressure. In particular, it is desirable if thetemperature of the product gas output from the reactor system is betweenabout 900° C. and 1100° C. or even up to 1300° C., and if the pressureof the product gas output from the reactor system is between about 30bar and about 100 bar. The invention will allow for precise control ofthe temperature of the product gas output from the reactor system.

An advantage of the invention is that the overall emission of carbondioxide and other emissions detrimental to the climate may be reducedconsiderably, in particular when the power used in the reactor system isfrom renewable energy resources.

SUMMARY OF THE INVENTION

The present invention is directed to a structured catalyst arranged forcatalyzing an endothermic reaction of a feed gas, said structuredcatalyst comprising a macroscopic structure of electrically conductivematerial, said macroscopic structure supporting a ceramic coating,wherein said ceramic coating supports a catalytically active material,wherein the electrically conductive material at least partly is acomposite in the form of a homogenous mixture of an electricallyconductive metallic material and a ceramic material, wherein themacroscopic structure at least partly is composed of two or morematerials with different resistivities.

The present invention is directed to the improvement of a structuredcatalyst of the type comprising a macroscopic structure of electricallyconductive material, wherein said macroscopic structure supports aceramic coating, and wherein said ceramic coating supports acatalytically active material.

The present invention is based on the finding that for a structuredcatalyst of the said type an electrically conductive material in theform of a homogenous mixture of an electrically conductive metallicmaterial and a ceramic material can be made to have a selected level ofresistivity, and that by using an electrically conductive material withan increased resistivity it is possible to increase the heat fluxthrough the material. The present invention has shown that by applying astructured catalyst with a higher resistivity as achieved by thecomposite material, an increased cross section of the structuredcatalyst can be used, which provides a possibility of reducing thenumber of structured catalysts required. This in turn reduces therequired number of monolith bridges and hence the number of connectionrequired to construct an array of the invention.

The invention is further based on the recognition that when using anelectrically conductive material in the form of the above mentionedcomposite material, it is possible to produce a structured catalyst,which has different resistivities and hence heat fluxes in the directionof feed gas flow through the catalyst. Such a design in turn allowsoptimization of the endothermic reaction to take place in the catalystto achieve a more efficient reaction.

The present invention further relates to a reactor system for carryingout an endothermic reaction of a feed gas, said reactor systemcomprising:

a) a catalyst of the invention;b) a pressure shell housing said catalyst, said pressure shellcomprising an inlet for letting in said feed gas and an outlet forletting out product gas, wherein said inlet is positioned so that saidfeed gas enters said catalyst in a first end and said product gas exitssaid catalyst from a second end; andc) a heat insulation layer between said structured catalyst and saidpressure shell.

The present invention further relates to use of the catalyst accordingto the invention or the reactor system of the invention, wherein theendothermic reaction is selected from the group consisting of steammethane reforming, hydrogen cyanide formation, methanol cracking,ammonia cracking, reverse water gas shift and dehydrogenation.

Definitions

In connection with the present invention the terms discussed below havethe flowing meanings:

The term “monolith” means a coherent structure with a well-definedsurface area, wherein “coherent” means a continuous phase.

The term “sintered treatment” means the process of compacting andforming a solid mass of material involving heating at least a part ofthe material to become mouldable or diffusible without melting thematerial to the point of liquefactions and then cooling the material tosolidify in its final form.

The term “hot spot” means a spot of an electrically conductivestructured catalyst material, wherein the material in the spot hasbecome highly heated due to local high current density transferring anelectrical energy to the spot, which significantly exceeds the energyrequired to drive a chemical reaction in the vicinity of the spot, andwherein there is a risk that the material become damaged due to theheating of the material to a temperature close to its melting point.

The term “resistivity” of a material means resistivity as measured bythe method comprising the steps of passing a fixed current is throughthe material, measuring the potential difference across said material,and correlating to the resistivity according to Ohm's law.Alternatively, other conventional methods well-known in the art may beused.

The term “at the first end” in relation where on a monolith a bridge isconnected means at a position on the monolith closer to the first endthan to the second end. The term “at the second end” in relation whereon a monolith a bridge is connected means at a position on the monolithcloser to the second end than to the first end.

The term “monolith bridge” means a bridge connecting two monoliths,wherein the bridge is a coherent structure, wherein “coherent” means acontinuous phase.

The term “composite in the form of a homogenous mixture” means amixture, which has the same proportion of its component throughout anygiven sample of the mixture.

The term “non-composite electrically conductive metallic material” meansan electrically conductive metallic material, which does not contain aceramic material.

The term “moldable state” means that the material is in a shapeablestate allowing the material to adhere and/or be integrated with anothermaterial in the same state. The term “current” includes both directcurrent and alternating current.

The term “green body” means a weakly bound, moldable material, e.g. inthe form of bonded powder, before sintering or oxidizing takes place.

The term “consists of a plurality of chemical elements” means at leastone chemical element.

Moreover, the term “steam reforming” is meant to denote a reformingreaction according to one or more of the following reactions:

CH₄+H₂O↔CO+3H₂  (i)

CH₄+2H₂O↔CO₂+4H₂  (ii)

CH₄+CO₂↔2CO+2H₂  (iii)

Reactions (i) and (ii) are steam methane reforming reactions, whilstreaction (iii) is the dry methane reforming reaction.

For higher hydrocarbons, viz. C_(n)H_(m), where n≥2, m≥4, equation (i)is generalized as:

C_(n)H_(m)+n H₂O↔nCO+(n+m/2)H₂  (iv)

-   -   where n≥2, m≥4.

Typically, steam reforming is accompanied by the water gas shiftreaction (v):

CO+H₂O↔CO₂+H₂  (v)

The term “steam methane reforming” is meant to cover the reactions (i)and (ii), the term “steam reforming” is meant to cover the reactions(i), (ii) and (iv), whilst the term “methanation” covers the reversereaction of reaction (i). In most cases, all of these reactions (i)-(v)are at, or close to, equilibrium at the outlet from the reactor system.The term “prereforming” is often used to cover the catalytic conversionof higher hydrocarbons according to reaction (iv). Prereforming istypically accompanied by steam reforming and/or methanation (dependingupon the gas composition and operating conditions) and the water gasshift reaction. Prereforming is often carried out in adiabatic reactorsbut may also take place in heated reactors.

The term “hydrogen cyanide synthesis” is meant to denote the followingreactions:

2CH₄+2NH₃+3O₂↔2HCN+6H₂O  (vi)

CH₄+NH₃↔HCN+3H₂  (vii)

The term “dehydrogenation” is meant to denote the following reaction:

R₁—CH₂-CH₂-R₂↔R₁—CH═CH—R₂  (viii)

Where R₁ and R₂ may be any appropriate group in a hydrocarbon molecule,such as —H, —CH₃, —CH₂, or —CH.

The term “methanol cracking” is meant to denote the following reactions:

CH₃OH↔CO+2H₂  (ix)

CH₃OH+H₂O↔CO₂+3H₂  (x)

Typically, methanol cracking reaction is accompanied by the water gasshift reaction (v).

The term “ammonia cracking” is meant to denote the following reactions:

2NH₃↔N₂+3H₂  (xi)

DETAILED DESCRIPTION OF THE INVENTION Structured Catalyst of a CompositeMaterial of the Invention

The present invention further relates to a structured catalyst arrangedfor catalyzing an endothermic reaction of a feed gas, said structuredcatalyst comprising a macroscopic structure of electrically conductivematerial, said macroscopic structure supporting a ceramic coating,wherein said ceramic coating supports a catalytically active material,wherein the electrically conductive material at least partly is acomposite of an electrically conductive metallic material and a ceramicmaterial, wherein the macroscopic structure at least partly is composedof two or more materials with different resistivities.

In a particular embodiment the macroscopic structure at least partly iscomposed of one or more composite materials and one or morenon-composite electrically conductive metallic materials. In aparticular embodiment the macroscopic structure at least partly iscomposed of two composite materials and one non-composite electricallyconductive metallic materials. In a particular embodiment themacroscopic structure at least partly is composed of two or morecomposite materials.

The electrically conductive metallic material of the said composite maybe any conventional catalytically active metallic material. In aparticular embodiment of the structured catalyst of the invention, themetallic material is an alloy comprising one or more substances selectedfrom the group consisting of Fe, Cr, Al, Co, Ni, Zr, Cu, Ti, Mn, and Si.

In a particular embodiment, the material of the macroscopic structure isselected from the group consisting of an alloy comprising iron andchromium, an alloy comprising iron, chromium and aluminum, an alloycomprising iron and cobalt, and an alloy comprising iron, aluminum,nickel, and cobalt. In a particular embodiment, the material of themacroscopic structure is a so-called “Alnico alloy”, which is a specifictype of alloy comprising iron, aluminum, nickel, and cobalt, andoptionally also copper, titanium. In a particular embodiment, thematerial of the macroscopic structure is a FeCrAlloy comprises iron,chromium and aluminum. In a particular embodiment, the material of themacroscopic structure is the alloy “Kanthal” comprising iron, chromiumand alumina. “Kanthal” has proven to be a good choice of material forthe macroscopic structure due to its resistive properties.

The ceramic material of the said composite may be any conventionalceramic material. In a particular embodiment of the structured catalystof the invention, the ceramic material is an oxide of a substanceselected from the group consisting of Al, Mg, Ce, Zr, Ca, Y and La. In aparticular embodiment of the structured catalyst of the invention, theceramic material is selected from the group consisting of Al2O3, ZrO2,MgAl2O3, ZrO2, MgAl2O3, CaAl2O3, any combination thereof and any of saidmaterials and combinations mixed with an oxide of Y, Ti, La, or Ce. In aparticular embodiment of the structured catalyst of the invention, theceramic material is selected from the group consisting of Al2O3, ZrO2,MgAl2O3, CaAl2O3, and any combination thereof. Ceramic oxides have a lowconductivity and hence have insulating properties. When added to anelectrically conductive metallic material, ceramic oxides will increasethe resistivity of the resulting composite material.

In a particular embodiment of the structured catalyst of the invention,the ratio based on weight of metallic material to ceramic material inthe macroscopic structure is in the range of from 50 to 1, preferablyfrom 40 to 1, more preferably from 30 to 2, more preferably from 24 to3, and most preferably from 19 to 4.

In a particular embodiment of the structured catalyst of the invention,the structured catalyst has the form of at least one monolith, whereinthe monolith has a number of flow channels formed therein for conveyingsaid feed gas through the monoliths from a first end, where the feed gasenters, to a second end, where a product gas exits, wherein saidmonolith has a longitudinal axis extending form said first end to saidsecond end.

In a particular embodiment of the structured catalyst of the invention,the macroscopic structure of the monolith is composed of two or morecomposite materials with different compositions positioned in thedirection of said longitudinal axis so as provide differentresistivities. In a particular embodiment of the structured catalyst ofthe invention, the macroscopic structure of the monolith is composed ofat least, three composite materials, preferably at least four compositematerials, more preferably at least five composite materials, morepreferably at least six composite materials, more preferably at leastseven composite materials, and most preferably at least eight compositematerials. In a particular embodiment of the structured catalyst of theinvention, the macroscopic structure of the monolith comprises at leasta first, a second and a third composite material positioned in thedirection from the first to the second end, wherein the second compositematerial has a higher resistivity as compared to the first and thirdcomposite material, the third composite material has a lower resistivityas compared to the first and second composite material, and the firstcomposite material has a resistivity in between the resistivity of thesecond and third composite material. Such design provides a structuredcatalyst with different heat fluxes which can be correlated to thechemical reactions in the channels. Having a low heat flux in the firstsection of the monolith allows for a balance in the supplied heattowards the chemical reaction rate, because the rate of reaction islower in the first end due to the lower temperatures in this end. Whenthe temperature increases as the gas in the channels travels towards thesecond end, it is an advantage to have a higher heat flux because thechemical rate of reaction in this zone is also higher and more reactantcan be consumed. At the second end of the monolith, it can be anadvantage to have a low heat flux again, because at this end the maximumtemperature is achieved, and controlling the temperature to a desiredoperating set point is made easier if the heat flux in this section islower.

In a particular embodiment of the structured catalyst of the invention,the macroscopic structure of the monolith is composed of one or morecomposite materials with different compositions and a non-compositeelectrically conductive metallic material positioned in the direction ofsaid longitudinal axis so as provide different resistivities.

In a particular embodiment of the structured catalyst of the invention,the macroscopic structure of the monolith is composed of two or more,preferably threes or more, more preferably four or more, more preferablyfive or more, more preferably six or more composite materials withdifferent compositions and a non-composite electrically conductivemetallic material positioned in the direction of said longitudinal axisso as provide different resistivities.

Preferably, the macroscopic structure of the monolith comprises at leasta first and a second composite material and a non-composite electricallyconductive metallic material positioned in the direction from the firstto the second end, wherein the second composite material has a higherresistivity as compared to the first composite material and thenon-composite material, the non-composite material has a lowerresistivity as compared to the first and second composite material, andthe first composite material has a resistivity in between theresistivity of the second composite material and the resistivity of thenon-composite material. The technical advantages of such a design arethe same as described in the preceding paragraph. The said embodiment ofthe structured catalyst is suitable for use in an array of theinvention, cf. below. In such an array the monolith bridge electricallyconductive material is preferably a non-composite electricallyconductive metallic material, e.g. the same non-composite material asused in the macroscopic structure.

Different resistivities of the composite material may be obtained bychanging one or more parameters selected from the group consisting of a)the ratio of the electrically conductive metallic material to theceramic material, b) the size of the ceramic particles, c) the shape ofthe ceramic particles, and d) the type of the ceramic material.

In a particular embodiment of the structured catalyst of the invention,the monolith composed of two or more composite materials with differentcompositions is produced by a method comprising the following steps:

-   -   preparing a plurality of pastes comprising:        -   at least a first paste having a first composition, wherein            the first paste comprises metal powder with a first alloy            composition, ceramic powder, and a first binder,        -   and at least a second paste having a second composition,            wherein the second paste (10 b) comprises metal powder with            a second alloy composition and a second binder    -   wherein the first alloy composition and the second alloy        composition both consist of a plurality of chemical elements,        and wherein the chemical elements are chosen so that, for each        of the chemical elements being present in an amount higher than        0.5 weight % of the respective alloy composition, that chemical        element is comprised both in the first and second alloy        composition, and        -   for the chemical elements being present in the first alloy            composition in amounts of up to 5.0 weight %, the amount of            that chemical element differs by at most 1 percentage point            between the first alloy composition and the second alloy            composition, and        -   for the chemical elements being present in the first alloy            composition in amounts of more than 5.0 weight %, the amount            of that chemical element differs by at most 3 percentage            point between the first alloy composition and the second            alloy composition,    -   transferring the plurality of pastes into a supply chamber of a        processing equipment,    -   shaping a green body from the plurality of pastes by forcing the        pastes from the supply chamber through a die of the processing        equipment, and    -   sintering or oxidizing the green body to obtain the composite        component having a varying resistivity (p) along a longitudinal        direction of the composite component, the longitudinal direction        corresponding to the direction of movement of the pastes through        the die, and the varying resistivity (p) resulting from the        first composition being different from the second composition.

In a particular embodiment of the structured catalyst of the invention,the catalyst is the array of the invention.

The present invention further relates to a structured catalyst arrangedfor catalyzing an endothermic reaction of a feed gas, said structuredcatalyst comprising a macroscopic structure of electrically conductivematerial, said macroscopic structure supporting a ceramic coating,wherein said ceramic coating supports a catalytically active material,wherein the electrically conductive material is a composite in the formof a homogenous mixture of an electrically conductive metallic materialand a ceramic material.

Array of the Catalyst of the Invention

In the present application the expression “array of the invention” means“array of the catalyst of the invention”, and the two expressions areused interchangeably.

The present invention further relates to an array comprising a first anda second structured catalyst of the invention, wherein:

a) the first and second structured catalyst have the form of a first andsecond monolith, respectively;b) each of said first and second monoliths has a number of flow channelsformed therein for conveying said feed gas through the monoliths from afirst end, where the feed gas enters, to a second end, where a productgas exits, wherein each of said first and second monoliths has alongitudinal axis extending from said first end to said secand end;c) the array comprises at least a first and a second conductorelectrically connected to said first and second monoliths, respectively,and to an electrical power supply, wherein said electrical power supplyis dimensioned to heat at least part of said first and second monolithsto a temperature of at least 500° C. by passing an electrical currentthrough said macroscopic structure, wherein said first conductor iselectrically connected directly or indirectly to the first monolith andthe second conductor is electrically connected directly or indirectly tothe second monolith, and wherein the conductors are connected atpositions on the array closer to said first end than to said second end,d) said first and second monolith are electrically connected by amonolith bridge of a monolith bridge electrically conductive material,e) the array is configured to direct an electrical current to run fromthe first conductor through the first monolith to said second end, thenthrough the bridge, and then through the second monolith to the secondconductor, andf) said array has been produced by a process comprising the steps ofi) providing the electrically conductive materials of the firstmonolith, the second monolith and the monolith bridge in the form ofthree separate entities, andii) joining the separate entities together by a method comprising a stepof sintering or oxidizing treatment.

The array of the present invention is constructed in such a way thatelectrical conductors, which supply electricity from the power supply,are connected at a position closest to the first end of the array of thestructured catalyst, but by the configurations of the monolith bridge(s)still directs current to run from substantially one end to the oppositeend of (most of) the individual monoliths. This feature establishes atemperature profile, where the temperature increases from the first endto the second end of the structured catalyst. This is advantageousbecause it provides a possibility of connecting the conductors to acolder end of this structured catalyst, a connection which is sensitiveto high temperatures. Also, this is advantageous because it allowsimproved control of the chemical reaction front of the endothermicreactions facilitated by the structured catalyst.

In a particular embodiment of the array of the invention, the secondconductor is connected directly to the second monolith. In thisconnection, the term “connected directly” means connected with nointermediate element, such as one or more monoliths. The connection ofthe conductor to the monolith may be a sintered connection or amechanical connection, such as by welding, soldering or brazing.

In a particular embodiment of the array of the invention, the secondconductor is indirectly electrically connected to the second monolith.In a particular embodiment of the array of the invention, the arrayfurther comprises (i) one or more juxtaposed additional intermediatemonoliths of a structured catalyst and (ii) one end monolith of astructured catalyst, wherein each additional intermediate monolith isconnected to at least two juxtaposed monoliths by a monolith bridge of amonolith bridge electrically conductive material, and wherein the endmonolith is connected to at least one juxtaposed monolith, and whereinthe second conductor is connected to the end monolith at a position onthe monolith closer to said first end than to said second end.Preferably, the total number of the additional intermediate monolithsand the end monolith is an even integer, and the second conductor isconnected to the end monolith at the first end of the array. Such adesign allows current to run from one end to the opposite end of eachmonolith. In the said particular embodiment of the array of theinvention, preferably the conductive material of the monolith bridges atthe second end of the array are the same material. In the saidparticular embodiment of the array of the invention, preferably theconductive materials of the monolith bridges are the same material.

In the particular embodiment of the invention, where the array comprisesone or more intermediate monoliths, the end monolith corresponds to thesecond monolith of the particular embodiment, where the array comprisesa first and a second monolith only. In this particular embodiment of theinvention, where the array comprises one or more intermediate monoliths,the second conductor is connected to the end monolith instead of thesecond monolith.

In a particular embodiment of the array of the invention, the totalnumber of the additional intermediate monoliths and the end monolith isany number between 3 and 36.

In a particular embodiment of the array of the invention, the first andsecond monolith are connected by the monolith bridge at the second endof the array, wherein each additional intermediate monolith is seriallyconnected to two juxtaposed monoliths by a monolith bridge of a monolithbridge electrically conductive material alternately at said first endand at said second end so as to direct the current from one end to theopposite end of each monolith, and wherein the end monolith is connectedto one juxtaposed monolith at the second end.

In a particular embodiment of the array of the invention, the said firstand second monolith are connected by the monolith bridge at the secondend of the array.

In a particular embodiment of the array of the invention, the electricalconnection between the first and second monolith by the monolith bridgeis a coherent connection, wherein in the zones, where the bridge hasbeen joined to the monoliths by the sintering or oxidizing treatment,the structure of the material is the same as that of the adjoiningmaterial in the monoliths and in the monolith bridge. Preferably, thereis no apparent interface in said joining zones. Alternatively, the term“coherently connected” may be defined as consistently intra-connected orconsistently coupled.

In a particular embodiment of the array of the invention, the monolithbridge extends over less than 50%, preferably 40%, more preferably 30%,more preferably 20%, and most preferably 10%, of the length from thefirst to the second end of the first and second monoliths.

In a particular embodiment of the array of the invention, said array hasbeen produced by a process of comprising the steps of

A) providing the electrically conductive materials of the firstmonolith, the second monolith and the monolith bridge in the form of twoor three separate entities, wherein the surface areas to be connected isin a moldable state,B) contacting the surface areas to be connected to form a continuousmaterial phase in the contact areas,C) joining the contact areas together by a method comprising a step ofsintering or oxidizing treatment.

In a particular embodiment of the array of the invention, the conductivematerials of the monoliths and the monoliths bridges are the samematerial.

In a particular embodiment of the array of the invention, at least oneof the electrically conductive materials of the monoliths and the atleast one monolith bridge is a composite of an electrically conductivemetallic material and of a ceramic material. It has been found that withthe said composite material, it is possible to obtain an increasedresistivity as compared to a material consisting solely of anelectrically conductive material. An increased resistivity allows for anincreased heating of the material.

In a particular embodiment of the array of the invention, theresistivity of at least one of the electrically conductive materials ofthe monoliths and the monolith bridges is from 1×10E-4 Ohm×m to 1×10E-7Ohm×m, preferably from 1×10E-5 Ohm×m to 1×10E-7 Ohm×m, more preferablyfrom 1×10E-5 Ohm×m to 5×10E-6 Ohm×m, and most preferably from 5×10E-5Ohm×m to 1×10E-6 Ohm×m.

In a particular embodiment of the array of the invention, the monolithbridge material is heat-resistant up to a temperature of at least 500°C., preferably at least 700° C., preferably at least 900° C., preferablyat least 1000° C., and most preferably at least 1100° C.

The endothermic reaction to be catalyzed by the array of the inventionmay be any endothermic chemical reaction, for which catalysis ispossible. In a particular embodiment of the array of the invention, theendothermic reaction is selected from the group consisting of steammethane reforming, hydrogen cyanide formation, methanol cracking,ammonia cracking, reverse water gas shift and dehydrogenation.

In a particular embodiment of the array of the invention, the monolithshave such a shape that the cross section in a plane perpendicular tosaid longitudinal axis is selected form the group consisting of apolygon, a regular polygon, a circle, a semi-circle, an oval, asemi-oval, a trapeze, and the monoliths may have the same or differentshapes.

In a particular embodiment of the array of the invention, the monolithshave such a shape that the cross section in a plane perpendicular tosaid longitudinal axis is a regular polygon selected from a triangle, arectangle, a pentagon, a hexagon, a heptagon, an octagon, a nonagon, adecagon, a hendecagon and a dodecagon. Preferably, the monoliths havethe same shape and such a shape that the cross section in a planeperpendicular to said longitudinal axis is selected from the groupconsisting of a triangle, a rectangle and a hexagon.

In a particular embodiment of the array of the invention, the flowchannels of the monoliths have such a shape that the cross section in aplane perpendicular to said longitudinal axis is selected from the groupconsisting of a polygon, a regular polygon, a circle, a semi-circle, anoval, a semi-oval, a trapeze, and the flow channels may have the same ordifferent shapes within one monolith and/or between different monoliths.

In a particular embodiment of the array of the invention, the flowchannels of the monoliths have such a shape that the cross section in aplane perpendicular to said longitudinal axis is a regular polygonselected from a triangle, a rectangle, a pentagon, a hexagon, aheptagon, an octagon, a nonagon, a decagon, a hendecagon and adodecagon. Preferably, the flow channels of the monoliths have the sameshape and such a shape that the cross section in a plane perpendicularto said longitudinal axis is selected from the group consisting of atriangle, a rectangle and a hexagon.

In a particular embodiment of the array of the invention, the array isconfigured to generate a heat flux of 500 to 50000 W/m² by resistanceheating of the material.

In a particular embodiment of the array of the invention, the array haselectrically insulating parts arranged to increase the length of aprincipal current path between said at least two conductors to a lengthlarger than the largest dimension of the monolith. In a particularembodiment of the array of the invention, said insulating parts have theform of slits in at least one of the monoliths. Preferably, the saidslits have a longitudinal direction perpendicular to the longitudinaldirection of the monoliths. In a particular embodiment of the invention,the electrically insulating parts are in the form of air or a materialwith a high resistivity, such as a ceramic. Preferably, the ratio of theresistivity of the conductive material of the monolith to theresistivity of the insulating part to is at least 50, preferably atleast 100, more preferably at least 200, more preferably at least 300,more preferably at least 400, more preferably at least 600, morepreferably at least 800, and most preferably at least 1000.

In a particular embodiment of the array of the invention, said array hasat least one electrically insulating part arranged to direct a currentthrough said monoliths in order to ensure that for at least 70% of thelength of said monoliths, a current density vector of the principalcurrent path has a non-zero component value parallel to the length ofsaid structured catalyst, i.e. parallel to the longitudinal axis of themonolith. Thus, for at least 70% of the length of the structuredcatalyst, the current density vector will have a positive or negativecomponent value parallel to the length of the structured catalyst. Thus,for at least 70%, e.g. for 90% or 95%, of the length of structuredcatalyst, viz. along the z-axis of the structured catalyst, the currentdensity vector of a principal current path will have a positive ornegative value along the z-axis. This means that the current is forcedfrom the first end of the structured catalyst towards the second end,and subsequently is forced towards the first end again. The temperatureof the gas entering the first end of the structured catalyst and theendothermic steam reforming reaction taking place over the structuredcatalyst absorbs heat from the structured catalyst. For this reason, thefirst end of the structured catalyst remains colder than the second end,and by ensuring that the current density vector of the principal currentpath has a non-zero component value parallel to the length of saidstructured catalyst, this takes place with a substantially continuouslyincreasing temperature profile, which gives a controllable reactionfront. In an embodiment the current density vector has a non-zerocomponent value parallel to the length of said structured catalyst in70% of the length of said structured catalyst, preferably 80%, morepreferably 90%, and even more preferably 95%. It should be noted thatthe term “the length of the structured catalyst” is meant to denote thedimension of the structured catalyst in the direction of the gas flow inthe reactor unit housing the structured catalyst.

In a particular embodiment of the array of the invention, a supportingpart is disposed in the space between juxtaposed monoliths, where thebridge is not present. The purpose of the supporting part is to supportthe array construction so as to avoid breakage or cracks from arising.In a particular embodiment of the array of the invention, the supportingpart is composed of a material with a high resistivity, such as aceramic. Preferably, the ratio of the resistivity of the conductivematerial of the monolith to the resistivity of the material of thesupporting part is at least 50, preferably at least 100, more preferablyat least 200, more preferably at least 300, more preferably at least400, more preferably at least 600, more preferably at least 800, andmost preferably at least 1000. In a particular embodiment of theinvention, the supporting part extends over at least 50%, preferably atleast 60%, more preferably at least 70%, more preferably at least 80%,and most preferably at least 90%, of the of the length from the first tothe second end of the monoliths not occupied by the bridge.

In a particular embodiment of the array of the invention, the length ofthe feed gas passage through the array is less than the length of thepassage of current from the first electrode through the array and to thesecond electrode.

In a particular embodiment of the array of the invention, the monolithbridge material is a material devoid of any space with a smallestdimension of 0.4 mm or more, preferably 0.6 mm or more, more preferably0.8 mm or more, more preferably 1.0 mm or more, more preferably 1.2 mmor more, more preferably 1.4 mm or more, more preferably 1.6 mm or more,more preferably 1.8 mm or more, and most preferably 2.0 mm or more,formed therein.

In a particular embodiment of the array of the invention, at least onemonolith is composed of at least two monolithic sections seriallyconnected by a section bridge of an section bridge electricallyconductive material. In a particular embodiment of the array of theinvention, said one monolith is composed of at least three monolithicsections, preferably at least four monolithic sections, more preferablyat least five monolithic sections, more preferably at least sixmonolithic sections, more preferably at least seven monolithic sections,and most preferably at least eight monolithic sections. In a particularembodiment of the array of the invention, said monolithic sections havedifferent resistivities. In a particular embodiment of the array of theinvention, said one monolith is composed of at least a first, a secondand a third monolithic section positioned in sequence in the directionfrom the first to the second end, wherein the second monolithic sectionhas a higher resistivity as compared to the first and third monolithicsection, the third monolithic section has a lower resistivity ascompared to the first and second monolithic section, and the firstmonolithic section has a resistivity in between the resistivity of thesecond and third composite material. Such design provides a temperatureprofile from the first end to the second end of the array, which isoptimized for the catalysis of the endothermic reaction.

Process for Producing Array

In a particular embodiment of the array of the invention, said array hasbeen produced by a process of comprising the steps of

A) providing the electrically conductive materials of the firstmonolith, the second monolith and the monolith bridge in the form of twoor three separate entities, wherein the surface areas to be connected isin a moldable state,B) contacting the surface areas to be connected to form a continuousmaterial phase in the contact areas,C) joining the contact areas together by a method comprising a step ofsintering or oxidizing treatment.

In a particular embodiment of the array of the invention, said array hasbeen produced by a process of comprising the steps of:

-   -   providing a first monolith component comprising metal powder        with a first alloy composition and a first soluble binder, the        first component having a first joining surface,    -   providing a second monolith component comprising metal powder        with a second alloy composition and a second soluble binder, the        second component having a second joining surface;    -   providing a bridge component comprising metal powder with a        third alloy composition and a third soluble binder, the bridge        component having two third joining surfaces, one at each end of        the bridge component;    -   wherein the first alloy composition and the second and third        alloy compositions all consist of a plurality of chemical        elements, and wherein the chemical elements are chosen so that,        for each of the chemical elements being present in an amount        higher than 0.5 weight % of the respective alloy composition,        that chemical element is comprised both in the first and second        and third alloy composition, and,        -   for the chemical elements being present in the first alloy            composition in amounts of up to 5.0 weight %, the amount of            that chemical element differs by at most 1 percentage point            between the first alloy composition on the one hand and each            of the second and third alloy compositions on the other            hand, and        -   for the chemical elements being present in the first alloy            composition in amounts of more than 5.0 weight %, the amount            of that chemical element differs by at most 3 percentage            point between the first alloy composition on the one hand            and each of the second and third alloy compositions on the            other hand,    -   arranging the bridge component between the first monolith        component and the second monolith component so that one third        joining surface contacts the first joining surface and that the        other third joining surface contacts the second joining surface,    -   maintaining the joining surfaces in contact for a time period        allowing for at least some evaporation of the solvent; and    -   subsequently sintering or oxidizing the first, second and third        components together while maintaining the joining surfaces in        contact or as close together as possible in order to achieve the        array.

In a particular embodiment of the above process, the following stepprecedes the step of arranging:

at least partly dissolving the first joining surface and/or the secondjoining surface by applying a solvent.

In a particular embodiment of the above process, the first, second andthird components are manufactured by powder extrusion, powder injectionmoulding, additive manufacturing, or tape casting.

In a particular embodiment of the above process, the metal alloycompositions of the first, second and third components comprise one ormore of the following: iron, chromium, aluminium, cobalt, nickel,manganese, molybdenum, vanadium, silicon or an alloy thereof.

In a particular embodiment of the above process, the first, secondand/or third component(s) comprises a ceramic material.

In a particular embodiment of the above process, the bridge componentcomprising dissolved binder and metal powder further comprises ceramicpowder.

In a particular embodiment of the above process, the first binder, thesecond binder, and the third binder have similar or the samesolvability, such as the first, second, and third binders being thesame.

In a particular embodiment of the above process, the binders of thefirst, second and/or third component(s) is dissoluble by water.

In a particular embodiment of the above process, after sintering oroxidizing former interfaces between the first monolith component, thesecond monolith component and the bridge component cannot be identifiedby use of Scanning Electron Microscopy analysis.

In a particular embodiment of the above process, a plurality of monolithcomponents and bridge components are joined together. In a particularembodiment of the above process, a plurality of monolith components andbridge components are joined together to produce an array with multiplemonoliths and bridges in a desired configuration.

Array with Element for Alleviating Adverse Effects Caused by Hot SpotFormation

In a particular embodiment of the array of the invention, the arrayfurther comprises an element for alleviating adverse effects caused byhot spot formation selected from the group consisting of:

-   -   (i) the two monoliths to be connected by the monolith bridge are        disposed so as to form a center plane positioned through the        geometric center of both of the two monoliths and positioned in        the same direction as the longitudinal axis of the array,        wherein the first and second monoliths have a first and a second        width in the direction perpendicular to said center plane,        wherein said monolith bridge has a width in the direction        perpendicular to said center plane, and wherein the width of the        monolith bridge is larger than said first and second widths,    -   (ii) the monolith bridge has a larger cross-sectional area at        one or both ends abutting the two monoliths to be connected than        at the center point of the bridge,    -   (iii) a safety bridge between monoliths, wherein the safety        bridge comprises a safety bridge electrically conductive        material having an electrical resistance, which is sufficient        high so as to restrain current from running through the safety        bridge when the monolith bridge is in operation, wherein the        safety bridge is positioned at any point between the first and        second end of the array;    -   (iv) a protrusion on at least one of the first and second        monolith for connecting the first and second conductor,        respectively, wherein the protrusion is of a protrusion        electrically conductive material;    -   (v) the monolith bridge material has a lower electrical        resistivity than the first electrically conductive material,    -   (vi) the monolith bridge comprises at least a first and a second        layer, wherein the first layer is positioned closer to the        second end of the array than the second layer, and wherein the        first layer has a lower electrical resistivity than the second        layer.

As explained above, a structured catalyst of the type of the presentinvention has a number of constructions parts (spots), wherein the flowof electrical current passing through the catalyst become restricted,because the current is forced to pass through a narrow passage with areduced cross section, e.g. at the second end of the structuredcatalyst, or to transfer from one section to another section, e.g. fromone type of material to another or across an interface between the twosections. There is a risk that such spots, which are sometimes referredto as hot spots, become over-heated and in turn are structurally damagedto become partly or wholly nonfunctional. The elements (i) to (vi) asdefined above each alleviate the risk of hot spot formation in differentconstruction parts of the array of the invention.

In a particular embodiment of the array of the invention withalleviating element (i) as defined above, the two monoliths to beconnected by the monolith bridge have a rectangular cross section in aplane perpendicular to said longitudinal axis and are arranged so as tohave parallel surfaces, wherein said two monoliths each have a frontsurface facing the other monolith, a back surface parallel to the frontsurface and two side surfaces perpendicular to the front and backsurfaces, wherein the monolith bridge comprises one or more of (A) aspacer section positioned between at least part of the front surfaces,(B) one or more side sections connected to at least part of one or moreof the side surfaces, and (C) a back section connected to at least partof the back surface and connected to at least one side section.

In a particular embodiment of the array of the invention, the bridge hasa form selected from the group consisting of an L-shaped body, anH-shaped body, a T-shaped body, an S-shaped body, an 8-shaped body, anO-shaped body, an F-formed body, an E-shaped body, and I-shaped body,two parallel linear bodies, and a rectangular frame body as viewed inthe direction of the longitudinal axis of the array, and wherein thebridge has a uniform dimension in the direction of the longitudinal axisof the array. In a particular embodiment of the array of the invention,each section of said bodies has a rectangular cross section in a planeperpendicular to the surface of the monolith to which the section isconnected. In a particular embodiment of the array of the invention, theside sections of the bridge each has a form of an elongated linear bodywith a longitudinal axis connecting the side surfaces of the twomonoliths to be connected and having a rectangular cross-section in adirection perpendicular to its longitudinal direction. In a particularembodiment of the array of the invention, the side section extends fromthe back surface of one monolith to the back surface of the secondmonolith. In a particular embodiment of the array of the invention, theelongated linear body at the surface closest to the first end of themonolith has extensions connected to the side surfaces of the monoliths.Preferably, the extensions have the form of a rectangular box as viewedin a direction perpendicular to the side surface. Alternatively, theextensions have the form of a box with a triangular cross-section asviewed in a direction perpendicular to the side surface, wherein thetriangle slopes from the back surface to the front surface.

In a particular embodiment of the array of the invention, the sidesections of the bridge each has the form of an elongated body with alongitudinal axis connecting the side surfaces of the two monoliths tobe connected and having a form as viewed from a direction perpendicularto the side surfaces with a straight line at the edge of the sidesection closest to the second end of the monoliths and with a curve inthe form of an partial ellipse at the edge of the side section closestto the first end of the monoliths, wherein the curve in the form of anpartial ellipse has a declining profile in a direction from the backsurfaces towards the front surfaces of the monoliths.

In a particular embodiment of the array of the invention withalleviating element (vi) as defined above, the monolith bridge containsone or more intermediate layers of an electrically conductive materialpositioned between the first and second layer, wherein the intermediatelayers have such electrical resistivities that the resistivity is atincreasing levels from layer to layer from the first layer to the secondlayer.

In a particular embodiment of the array of the invention withalleviating element (vi) as defined above, the first layer has a lowerresistivity than the resistivity of the first electrically conductivematerial, and the second layer has a higher resistivity than the firstelectrically conductive material.

Endothermic Reactions

In an embodiment, the endothermic reaction is dehydrogenation ofhydrocarbons. This reaction takes place according to reaction (viii).The catalyst material for the reaction may be Pt/Al₂O₃ or Pt—Sn/Al₂O₃.The catalytically active material may be Pt. The maximum temperature ofthe reactor may be between 500-700° C. The pressure of the feed gas maybe 2-5 bar.

In an embodiment, the endothermic reaction is cracking of methanol. Thisreaction takes place according to reaction (v), (ix), and (x). Thecatalyst material for the reaction may be Ni/MgAl₂O₃ or Cu/Zn/Al₂O₃. Thecatalytically active material may be Cu or Ni. The maximum temperatureof the reactor may be between 200-300° C. The pressure of the feed gasmay be 2-30 bar, preferably about 25 bar.

In an embodiment, the endothermic reaction is cracking of methanol. Thecatalyst material for the reaction may be CuZnO/Al2O3,Fe/Al2O3NiGa/MgAl2O4, or CuZn/ZrO2. The catalytically active materialmay be Cu, Zn, ZnO, Fe, Ga, Ni, or a combination thereof, while theceramic coating may be Al2O3, ZrO2, MgAl2O3, CaAl2O3, or a combinationtherefore and potentially mixed with oxides of Y, Ti, La, or Ce. Themaximum temperature of the reactor may be between 150-1300° C. Thepressure of the feedstock may be 2-200 bar, preferably about 25 bar. Inan embodiment said macroscopic structure is made of an alloy of Fe CrAl, supporting a ceramic coating of a ZrO2 and Al₂O₃ mixture, with CuZnas catalytically active material. In another embodiment, saidmacroscopic structure is made of an alloy of Fe Cr Al, supporting aceramic coating of a ZrO2 and MgAl2O4 mixture, with Ni as catalyticallyactive material. In another embodiment, said macroscopic structure ismade of an alloy of Fe Cr Al, supporting a ceramic coating of a ZrO2,with Mn as catalytically active material.

In an embodiment, the endothermic reaction is steam reforming ofhydrocarbons. This reaction takes place according to reaction (i)-(v).The catalyst material for the reaction may be Ni/Al₂O₃, Ni/MgAl₂O₃,Ni/CaAl₂O₃, Ru/MgAl₂O₃, or Rh/MgAl₂O₃. The catalytically active materialmay be Ni, Ru, Rh, Ir, or a combination thereof. The maximum temperatureof the reactor may be between 850-1300° C. The pressure of the feed gasmay be 15-180 bar, preferably about 25 bar.

In an embodiment, the endothermic reaction is steam reforming ofhydrocarbons. The catalyst material for the reaction may be Ni/Al2O3,Ni/ZrO2, Ni/MgAl2O3, Ni/CaAl2O3, Ru/MgAl2O3, or Rh/MgAl2O3. Thecatalytically active material may be Ni, Ru, Rh, Ir, or a combinationthereof, while the ceramic coating may be Al2O3, ZrO2, MgAl2O3, CaAl2O3,or a combination therefore and potentially mixed with oxides of Y, Ti,La, or Ce. The maximum temperature of the reactor may be between850-1300° C. The pressure of the feed gas may be 15-180 bar, preferablyabout 25 bar. In an embodiment said macroscopic structure is made of analloy of Fe Cr Al, supporting a ceramic coating of a ZrO2 and MgAl2O4mixture, with nickel as catalytically active material.

In an embodiment, the endothermic reaction is ammonia cracking. Thisreaction takes place according to reaction (xi). The catalyst materialfor the reaction may be Fe, FeCo, or Ru/Al₂O₃. The catalytically activematerial may be Fe or Ru. The maximum temperature of the reactor may bebetween 400-700° C. The pressure of the feed gas may be 2-30 bar,preferably about 25 bar.

In an embodiment, the endothermic reaction is ammonia cracking. Thecatalyst material for the reaction may be Fe (prepared from Fe3O4 orFeO), FeCo, Ru/Al2O3, Ru/ZrO2, Fe/Al2O3, FeCo/Al2O3, Ru/MgAl2O3, orCoSn/Al2O3. The catalytically active material may be Ru, Rh, Fe, Co, Ir,Os, or a combination thereof, while the ceramic coating may be Al2O3,ZrO2, MgAl2O3, CaAl2O3, or a combination therefore and potentially mixedwith oxides of Y, Ti, La, or Ce. The maximum temperature of the reactormay be between 300-1300° C. The pressure of the feed gas may be 2-180bar, preferably about 25 bar. In an embodiment said macroscopicstructure is made of an alloy of Fe Cr Al, supporting a ceramic coatingof a ZrO2 and Al2O3 mixture, with Ru as catalytically active material.

In an embodiment, the endothermic reaction is the hydrogen cyanidesynthesis or a synthesis process for organic nitriles. This reactiontakes place according to reaction (vi) and (vii). The catalyst materialfor the reaction may be Pt/Al₂O₃. The catalytically active material maybe Pt, Co, or SnCo. The maximum temperature of the reactor may bebetween 700-1200° C. The pressure of the feed gas may be 2-30 bar,preferably about 5 bar.

In an embodiment, the endothermic reaction is the hydrogen cyanidesynthesis or a synthesis process for organic nitriles. The catalystmaterial for the reaction may be Pt/Al2O3, Pt/ZrO2, Ru/Al2O3, Rh/Al2O3,Pt/MgAl2O4, or CoSn/Al2O3. The catalytically active material may be Pt,Ru, Rh, Ir, Co, Sn, or a combination thereof, while the ceramic coatingmay be Al₂O₃, ZrO2, MgAl2O4, CaAl2O4, or a combination therefore andpotentially mixed with oxides of Y, Ti, La, or Ce. The maximumtemperature of the reactor may be between 850-1300° C. The pressure ofthe feed gas may be 2-180 bar, preferably about 25 bar. In an embodimentsaid macroscopic structure is made of an alloy of Fe Cr Al, supporting aceramic coating of a ZrO2 and Al2O3 mixture, with Pt as catalyticallyactive material.

In an embodiment, the endothermic reaction is aromatization ofhydrocarbons. This is advantageously aromatization of higherhydrocarbons.

Reactor of the Invention

The invention further relates to a reactor system for carrying out anendothermic reaction of a feed gas, said reactor system comprising:

a) a catalyst of the present invention or an array of the invention;b) a pressure shell housing said catalyst, said pressure shellcomprising an inlet for letting in said feed gas and an outlet forletting out product gas, wherein said inlet is positioned so that saidfeed gas enters said catalyst in a first end and said product gas exitssaid catalyst from a second end; andc) a heat insulation layer between said structured catalyst and saidpressure shell.

Use of the Catalyst of the Invention

The present invention further relates to the use of the catalystaccording to the invention, the array of the invention or the reactor ofthe invention, wherein the endothermic reaction is selected from thegroup consisting of steam methane reforming, hydrogen cyanide formation,methanol cracking, ammonia cracking, reverse water gas shift anddehydrogenation.

Items of the Invention

1. A structured catalyst arranged for catalyzing an endothermic reactionof a feed gas, said structured catalyst comprising a macroscopicstructure of electrically conductive material, said macroscopicstructure supporting a ceramic coating, wherein said ceramic coatingsupports a catalytically active material, wherein the electricallyconductive material at least partly is a composite in the form of ahomogenous mixture of an electrically conductive metallic material and aceramic material, wherein the macroscopic structure at least partly iscomposed of two or more materials with different resistivities.

2. Catalyst according to item 1, wherein the macroscopic structure atleast partly is composed of one or more composite materials and one ormore non-composite electrically conductive metallic materials.

3. Catalyst according to any of items 1-2, wherein the metallic materialis an alloy comprising one or more substances selected from the groupconsisting of Fe, Cr, Al, Co, Ni, Zr, Cu, Ti, Mn, and Si.

4. Catalyst according to any of items 1-3, wherein the ceramic materialis an oxide of a substance selected from the group consisting of Al, Mg,Ce, Zr, Ca, Y and La.

5. Catalyst according to any of items 1-4, wherein the ratio based onweight of metallic material to ceramic material in the macroscopicstructure is in the range of from 50 to 1, preferably from 40 to 1, morepreferably from 30 to 2, more preferably from 24 to 3, and mostpreferably from 19 to 4.

6. Catalyst according to any of items 2-5, wherein the structuredcatalyst has the form of at least one monolith, wherein the monolith hasa number of flow channels formed therein for conveying said feed gasthrough the monoliths from a first end, where the feed gas enters, to asecond end, where a product gas exits, wherein said monolith has alongitudinal axis extending form said first end to said second end.

7. Catalyst according to item 6, wherein the macroscopic structure ofthe monolith is composed of two or more composite materials withdifferent compositions positioned in the direction of said longitudinalaxis so as provide different resistivities.

8. Catalyst according to item 7, wherein the macroscopic structure ofthe monolith is composed of at least, three composite materials,preferably at least four composite materials, more preferably at leastfive composite materials, more preferably at least six compositematerials, more preferably at least seven composite materials, and mostpreferably at least eight composite materials.

9. Catalyst according to item 8, wherein the macroscopic structure ofthe monolith comprises at least a first, a second and a third compositematerial positioned in the direction from the first to the second end,wherein the second composite material has a higher resistivity ascompared to the first and third composite material, the third compositematerial has a lower resistivity as compared to the first and secondcomposite material, and the first composite material has a resistivityin between the resistivity of the second and third composite material.

10. Catalyst according to item 6, wherein the macroscopic structure ofthe monolith is composed of one or more composite materials withdifferent compositions and a non-composite electrically conductivemetallic material positioned in the direction of said longitudinal axisso as provide different resistivities.

11. Catalyst according to item 10, wherein the macroscopic structure ofthe monolith comprises at least a first and a second composite materialand a non-composite electrically conductive metallic material positionedin the direction from the first to the second end, wherein the secondcomposite material has a higher resistivity as compared to the firstcomposite material and the non-composite material, the non-compositematerial has a lower resistivity as compared to the first and secondcomposite material, and the first composite material has a resistivityin between the resistivity of the second composite material and theresistivity of the non-composite material.

12. Array comprising a first and a second structured catalyst accordingto any of items 1-11, wherein:

a) the first and second structured catalyst have the form of a first andsecond monolith, respectively;b) each of said first and second monoliths has a number of flow channelsformed therein for conveying said feed gas through the monoliths from afirst end, where the feed gas enters, to a second end, where a productgas exits, wherein each of said first and second monoliths has alongitudinal axis extending from said first end to said second end;c) the array comprises at least a first and a second conductorelectrically connected to said first and second monoliths, respectively,and configured to be connected to an electrical power supply, whereinsaid electrical power supply is dimensioned to heat at least part ofsaid first and second monoliths to a temperature of at least 500° C. bypassing an electrical current through said macroscopic structure,wherein said first conductor is electrically connected directly orindirectly to the first monolith and the second conductor iselectrically connected directly or indirectly to the second monolith,and wherein the conductors are connected at positions on the arraycloser to said first end than to said second end,d) said first and second monolith are electrically connected by amonolith bridge of a monolith bridge electrically conductive material,e) the array is configured to direct an electrical current to run fromthe first conductor through the first monolith to said second end, thenthrough the bridge, and then through the second monolith to the secondconductor, andf) said array has been produced by a process comprising the steps ofi) providing the electrically conductive materials of the firstmonolith, the second monolith and the monolith bridge in the form ofthree separate entities, andii) joining the separate entities together by a method comprising a stepof sintering or oxidizing treatment.

13. Array according to item 12, wherein the second conductor isconnected directly to the second monolith.

14. Array according to item 13, wherein the second conductor isindirectly electrically connected to the second monolith.

15. Array according to item 14, wherein the array further comprises (i)one or more juxtaposed additional intermediate monoliths of a structuredcatalyst and (ii) one end monolith of a structured catalyst, whereineach additional intermediate monolith is connected to at least twojuxtaposed monoliths by a monolith bridge of a monolith bridgeelectrically conductive material, and wherein the end monolith isconnected to at least one juxtaposed monolith, and wherein the secondconductor is connected to the end monolith at a position on the monolithcloser to said first end than to said second end.

16. Array according to item 15, wherein the total number of theadditional intermediate monoliths and the end monolith is an eveninteger, and wherein the second conductor is connected to the endmonolith at the first end of the array.

17. Array according to item 16, wherein the first and second monolithare connected by the monolith bridge at the second end of the array,wherein each additional intermediate monolith is serially connected totwo juxtaposed monoliths by a monolith bridge of a monolith bridgeelectrically conductive material alternately at said first end and atsaid second end so as to direct the current from one end to the oppositeend of each monolith, and wherein the end monolith is connected to onejuxtaposed monolith at the second end.

18. Array according to any of items 12-17, wherein the said first andsecond monolith are connected by the monolith bridge at the second endof the array.

19. Array according to any of items 12-18, wherein the monolith bridgeextends over less than 50%, preferably 40%, more preferably 30%, morepreferably 20%, and most preferably 10%, of the length from the first tothe second end of the first and second monoliths.

20. Array according to any of items 12-19, wherein said array has beenproduced by a process of comprising the steps of

A) providing the electrically conductive materials of the firstmonolith, the second monolith or the intermediate monolith and themonolith bridge in the form of three separate entities, wherein thesurface areas to be connected are in a moldable state,B) contacting the surface areas to be connected in the contact areas,C) joining the contact areas together by a method comprising a step ofsintering or oxidizing treatment.

21. Array according to any of items 12-20, wherein said array has beenproduced by a process of comprising the steps of:

-   -   providing a first monolith component comprising metal powder        with a first alloy composition and a first soluble binder, the        first component having a first joining surface,    -   providing a second monolith component comprising metal powder        with a second alloy composition and a second soluble binder, the        second component having a second joining surface;    -   providing a bridge component comprising metal powder with a        third alloy composition and a third soluble binder, the bridge        component having two third joining surfaces, one at each end of        the bridge component;    -   wherein the first alloy composition and the second and third        alloy compositions all consist of a plurality of chemical        elements, and wherein the chemical elements are chosen so that,        for each of the chemical elements being present in an amount        higher than 0.5 weight % of the respective alloy composition,        that chemical element is comprised both in the first and second        and third alloy composition, and        -   for the chemical elements being present in the first alloy            composition in amounts of up to 5.0 weight %, the amount of            that chemical element differs by at most 1 percentage point            between the first alloy composition on the one hand and each            of the second and third alloy compositions on the other            hand, and        -   for the chemical elements being present in the first alloy            composition in amounts of more than 5.0 weight %, the amount            of that chemical element differs by at most 3 percentage            point between the first alloy composition on the one hand            and each of the second and third alloy compositions on the            other hand,    -   arranging the bridge component between the first monolith        component and the second monolith component so that one third        joining surface contacts the first joining surface and that the        other third joining surface contacts the second joining surface,    -   maintaining the joining surfaces in contact for a time period        allowing for at least some evaporation of the solvent; and    -   subsequently sintering or oxidizing the first, second and third        components together while maintaining the joining surfaces in        contact or as close together as possible in order to achieve the        array.

22. Array according to item 21, wherein the following step precedes thestep of arranging:

-   -   at least partly dissolving the first joining surface and/or the        second joining surface by applying a solvent.

23. Array according to any of items 15-22, wherein the conductivematerials of the monolith bridges are the same material.

24. Array according to any of items 15-23, wherein the conductivematerial of the monolith bridges at the second end of the array are thesame material.

25. Array according to any of items 12-24, wherein the conductivematerials of the monoliths and the monoliths bridges are the samematerial.

26. Array according to any items 12-25, wherein at least one of theelectrically conductive materials of the monoliths and of the at leastone monolith bridge is a composite of an electrically conductivemetallic material and a ceramic material.

27. Array according to any of items 12-26, wherein the resistivity of atleast one of the electrically conductive materials of the monoliths andthe monolith bridges is from 1×10E-4 Ohm×m to 1×10E-7 Ohm×m, preferablyfrom 1×10E-5 Ohm×m to 1×10E-7 Ohm×m, more preferably from 1×10E-5 Ohm×mto 5×10E-6 Ohm×m, and most preferably from 5×10E-5 Ohm×m to 1×10E-6Ohm×m.

28. Array according to any of items 12-27, wherein the monolith bridgematerial is heat-resistant up to a temperature of at least 500° C.,preferably at least 700° C., preferably at least 900° C., preferably atleast 1000° C., and most preferably at least 1100° C.

29. Array according to any of items 12-28, wherein the endothermicreaction is selected from the group consisting of steam methanereforming, hydrogen cyanide formation, methanol cracking, ammoniacracking, reverse water gas shift and dehydrogenation.

30. Array according to any of items 12-29, wherein the monoliths havesuch a shape that the cross section in a plane perpendicular to saidlongitudinal axis is selected form the group consisting of a polygon, aregular polygon, a circle, a semi-circle, an oval, a semi-oval, atrapeze, and wherein the monoliths may have the same or differentshapes.

31. Array according to item 30, wherein the monoliths have such a shapethat the cross section in a plane perpendicular to said longitudinalaxis is a regular polygon selected from a triangle, a rectangle, apentagon, a hexagon, a heptagon, an octagon, a nonagon, a decagon, ahendecagon and a dodecagon.

32. Array according to any of items 12-31, wherein the array furthercomprises an element for alleviating adverse effects caused by hot spotformation selected from the group consisting of:

-   -   (i) the two monoliths connected by the monolith bridge are        disposed so as to form a center plane positioned through the        geometric center of both of the two monoliths and positioned        parallel to the longitudinal axis of the array, wherein the        first and second monoliths have a first and a second width in        the direction perpendicular to said center plane, wherein said        monolith bridge has a width in the direction perpendicular to        said center plane, and wherein the width of the monolith bridge        is larger than said first and second widths,    -   (ii) the monolith bridge has a larger cross-sectional area at        one or both ends abutting the two monoliths to be connected than        at the center point of the bridge,    -   (iii) a safety bridge between monoliths, wherein the safety        bridge comprises a safety bridge electrically conductive        material having an electrical resistance, which is sufficient        high so as to restrain current from running through the safety        bridge when the monolith bridge is in operation, wherein the        safety bridge is positioned at any point between the first and        second end of the array;    -   (iv) a protrusion on at least one of the first and second        monolith for connecting the first and second conductor,        respectively, wherein the protrusion is of a protrusion        electrically conductive material;    -   (v) the monolith bridge material has a lower electrical        resistivity than the first electrically conductive material,    -   (vi) the monolith bridge comprises at least a first and a second        layer, wherein the first layer is positioned closer to the        second end of the array than the second layer, and wherein the        first layer has a lower electrical resistivity than the second        layer.

33. Array according to item 32 (i), the two monoliths to be connected bythe monolith bridge have a rectangular cross section in a planeperpendicular to said longitudinal axis and are arranged so as to haveparallel surfaces, wherein said two monoliths each have a front surfacefacing the other monolith, a back surface parallel to the front surfaceand two side surfaces perpendicular to the front and back surfaces,wherein the monolith bridge comprises one or more of (A) a spacersection positioned between at least part of the front surfaces, (B) oneor more side sections connected to at least part of one or more of theside surfaces, and (C) a back section connected to at least part of theback surface and connected to at least one side section.

34. Array according to item 33, wherein the bridge has a form selectedfrom the group consisting of an L-shaped body, an H-shaped body, aT-shaped body, an S-shaped body, an 8-shaped body, an O-shaped body, anF-formed body, an E-shaped body, and I-shaped body, two parallel linearbodies, and a rectangular frame body as viewed in the direction of thelongitudinal axis of the array, and wherein the bridge has a uniformdimension in the direction of the longitudinal axis of the array.

35. Array according to item 34, wherein each section of said bodies hasa rectangular cross section in a plane perpendicular to the surface ofthe monolith to which the section is connected.

36. Array according to item 33, wherein the side sections of the bridgeeach has a form of an elongated linear body with a longitudinal axisconnecting the side surfaces of the two monoliths to be connected andhaving a rectangular cross-section in a direction perpendicular to itslongitudinal direction.

37. Array according to item 35 or 36, wherein the side section extendsfrom the back surface of one monolith to the back surface of the secondmonolith.

38. Array according to any of items 35-37, wherein the elongated linearbody at the surface closest to the first end of the monolith hasextensions connected to the side surfaces of the monoliths.

39. Array according to item 38, wherein the extensions have the form ofa rectangular box as viewed in a direction perpendicular to the sidesurface.

40. Array according to item 39, wherein the extensions have the form ofa box with a triangular cross-section as viewed in a directionperpendicular to the side surface, wherein the triangle slopes from theback surface to the front surface.

41. Array according to item 33, wherein the side sections of the bridgeeach has the form of an elongated body with a longitudinal axisconnecting the side surfaces of the two monoliths to be connected andhaving a form as viewed from a direction perpendicular to the sidesurfaces with a straight line at the edge of the side section closest tothe second end of the monoliths and with a curve in the form of anpartial ellipse at the edge of the side section closest to the first endof the monoliths, wherein the curve in the form of an partial ellipsehas a declining profile in a direction from the back surfaces towardsthe front surfaces of the monoliths.

42. Array according to item 32 (vi), wherein the monolith bridgecontains one or more intermediate layers of an electrically conductivematerial positioned between the first and second layer, wherein theintermediate layers have such electrical resistivities that theresistivity is at increasing levels from layer to layer from the firstlayer to the second layer.

43. Array according to item 32 (vi), wherein the first layer has a lowerresistivity than the resistivity of the first electrically conductivematerial, and wherein the second layer has a higher resistivity than thefirst electrically conductive material.

44. Array according to any of items 12-43, wherein the array isconfigured to generate a heat flux of 500 to 50000 W/m² by resistanceheating of the material.

45. Array according to any of items 12-44, wherein the array haselectrically insulating parts arranged to increase the length of aprincipal current path between said at least two conductors to a lengthlarger than the largest dimension of the monolith.

46. Array according to any of items 12-45, wherein said array has atleast one electrically insulating part arranged to direct a currentthrough said monoliths in order to ensure that for at least 70% of thelength of said monoliths, a current density vector of the principalcurrent path has a non-zero component value parallel to the length ofsaid structured catalyst.

47. Array according to any of items 12-46, wherein the length of thefeed gas passage through the array is less than the length of thepassage of current from the first electrode through the array and to thesecond electrode.

48. Array according to any of items 12-47, wherein the monolith bridgematerial is a material devoid of any space with a smallest dimension of0.4 mm or more, preferably 0.6 mm or more, more preferably 0.8 mm ormore, more preferably 1.0 mm or more, more preferably 1.2 mm or more,more preferably 1.4 mm or more, more preferably 1.6 mm or more, morepreferably 1.8 mm or more, and most preferably 2.0 mm or more, formedtherein.

49. Array according to any of items 12-48, wherein the flow channels ofthe monoliths have such a shape that the cross section in a planeperpendicular to said longitudinal axis is selected from the groupconsisting of a polygon, a regular polygon, a circle, a semi-circle, anoval, a semi-oval, a trapeze, and wherein the flow channels may have thesame or different shapes within one monolith and/or between differentmonoliths.

50. Array according to item 49, wherein the flow channels of themonoliths have such a shape that the cross section in a planeperpendicular to said longitudinal axis is a regular polygon selectedfrom a triangle, a rectangle, a pentagon, a hexagon, a heptagon, anoctagon, a nonagon, a decagon, a hendecagon and a dodecagon.

51. A reactor system for carrying out an endothermic reaction of a feedgas, said reactor system comprising:

a) a catalyst of any of item 1-11 or the array of any of items 12-50;b) a pressure shell housing said array, said pressure shell comprisingan inlet for letting in said feed gas and an outlet for letting outproduct gas, wherein said inlet is positioned so that said feed gasenters said array in a first end and said product gas exits said arrayfrom a second; andc) a heat insulation layer between said structured catalyst and saidpressure shell.

52. Use of the catalyst according to any of items 1-11 or the array ofany of items 12-50 or the reactor system of claim 51, wherein theendothermic reaction is selected from the group consisting of steammethane reforming, hydrogen cyanide formation, methanol cracking,ammonia cracking, reverse water gas shift and dehydrogenation.

Points of the Invention

1. A structured catalyst arranged for catalyzing an endothermic reactionof a feed gas, said structured catalyst comprising a macroscopicstructure of electrically conductive material, said macroscopicstructure supporting a ceramic coating, wherein said ceramic coatingsupports a catalytically active material, wherein the electricallyconductive material is a composite in the form of a homogenous mixtureof an electrically conductive metallic material and a ceramic material.

1.1. Catalyst according to point 1 wherein the electrically conductivematerial is a composite comprising different materials having differentcompositions, wherein one or more of the compositions comprise metallicmaterial and ceramic material, and wherein the different materials arepositioned in a way so as to provide varying resistivity in thedirection of a longitudinal axis of the macroscopic structure of themonolith.

2. Catalyst according to point 1, wherein the metallic material is analloy comprising one or more substances selected from the groupconsisting of Fe, Cr, Al, Co, Ni, Zr, Cu, Ti, Mn, and Si.

3. Catalyst according to any of points 1-2, wherein the ceramic materialis an oxide of a substance selected from the group consisting of Al, Mg,Ce, Zr, Ca, Y and La.

4. Catalyst according to any of point 1-3, wherein the ratio based onweight of metallic material to ceramic material in the macroscopicstructure is in the range of from 50 to 1, preferably from 40 to 1, morepreferably from 30 to 2, more preferably from 24 to 3, and mostpreferably from 19 to 4.

5. Catalyst according to point 1 or any of points 2-4, wherein thestructured catalyst has the form of at least one monolith, wherein themonolith has a number of flow channels formed therein for conveying saidfeed gas through the monoliths from a first end, where the feed gasenters, to a second end, where a product gas exits, wherein saidmonolith has a longitudinal axis extending form said first end to saidsecond end.

6. Catalyst according to point 5, wherein the macroscopic structure ofthe monolith is composed of two or more composite materials withdifferent compositions positioned in the direction of said longitudinalaxis so as provide different resistivities.

6.1 Catalyst according to any of the points 1 to 5, wherein themacroscopic structure of the monolith comprises more than one compositematerials comprising different compositions, wherein differentcompositions are positioned in the direction of the longitudinal axis ofthe monolith so as to provide different resistivities changing along thelongitudinal axis of the monolith.

6.2. The macroscopic structure of the monolith of any of points above,manufactured from a plurality of pastes of different compositions mayconstitute a composite component itself resulting from differentmaterials of each of the pastes. In such an embodiment, macroscopicstructure of the monolith is a composite comprising different materialsresulted from different compositions of the pastes, wherein one or moreof the pastes may have a composition different than the other, andwherein the different materials are positioned in a way so as to providevarying resistivity in the direction of a longitudinal axis of themacroscopic structure of the monolith.

6.3. In an embodiment, the macroscopic structure of the monolithaccording to any of points above may comprise at least partly one ormore alloys and at least partly one or more alloys with ceramicparticles, resulting from different compositions used to prepareplurality of pastes, wherein different parts are positioned in thedirection of said longitudinal axis, as described in the method ofproducing the monolith.

7. Catalyst according to point 6, wherein the macroscopic structure ofthe monolith is composed of at least, three composite materials,preferably at least four composite materials, more preferably at leastfive composite materials, more preferably at least six compositematerials, more preferably at least seven composite materials, and mostpreferably at least eight composite materials.

8. Catalyst according to point 7, wherein the macroscopic structure ofthe monolith comprises at least a first, a second and a third compositematerial positioned in the direction from the first to the second end,wherein the second composite material has a higher resistivity ascompared to the first and third composite material, the third compositematerial has a lower resistivity as compared to the first and secondcomposite material, and the first composite material has a resistivityin between the second and third composite material.

9. Array comprising a first and a second structured catalyst accordingto any of points 1-8 wherein:

a) the first and second structured catalyst have the form of a first anda second monolith respectivelyb) each of said first and second monoliths has a number of flow channelsformed therein for conveying said feed gas through the monoliths from afirst end, where the feed gas enters, to a second end, where a productgas exits, wherein each of said first and second monoliths has alongitudinal axis extending from said first end to said second end;c) the array comprises at least a first and a second conductorelectrically connected to said first and second monoliths, respectively,and configured to be connected to an electrical power supply, whereinsaid electrical power supply is dimensioned to heat at least part ofsaid first and second monoliths to a temperature of at least 500° C. bypassing an electrical current through said macroscopic structure,wherein said first conductor is electrically connected directly orindirectly to the first monolith and the second conductor iselectrically connected directly or indirectly to the second monolith,and wherein the conductors are connected at positions on the arraycloser to said first end than to said second end,d) said first and second monolith are electrically connected by amonolith bridge of a monolith bridge electrically conductive material,e) the array is configured to direct an electrical current to run fromthe first conductor through the first monolith to said second end, thenthrough the bridge, and then through the second monolith to the secondconductor, andf) said array has been produced by a process comprising the steps ofi) providing the electrically conductive materials of the firstmonolith, the second monolith and the monolith bridge in the form ofthree separate entities, andii) joining the separate entities together by a method comprising a stepof sintering or oxidizing treatment.

10. Array according to point 9, wherein the second conductor isconnected directly to the second monolith.

11. Array according to point 9, wherein the second conductor isindirectly electrically connected to the second monolith.

12. Array according to point 10 or 11, wherein the array furthercomprises (i) one or more juxtaposed additional intermediate monolithsof a structured catalyst and (ii) one end monolith of a structuredcatalyst, wherein each additional intermediate monolith is connected toat least two juxtaposed monoliths by a monolith bridge of a monolithbridge electrically conductive material, and wherein the end monolith isconnected to at least one juxtaposed monolith, and wherein the secondconductor is connected to the end monolith at a position on the monolithcloser to said first end than to said second end.

13. Array according to item 12, wherein the total number of theadditional intermediate monoliths and the end monolith is an eveninteger, and wherein the second conductor is connected to the endmonolith at the first end of the array.

14. Array according to point 13, wherein the first and second monolithare connected by the monolith bridge at the second end of the array,wherein each additional intermediate monolith is serially connected totwo juxtaposed monoliths by a monolith bridge of a monolith bridgeelectrically conductive material alternately at said first end and atsaid second end so as to direct the current from one end to the oppositeend of each monolith, and wherein the end monolith is connected to onejuxtaposed monolith at the second end.

15. Array according to any of points 9-14, wherein the said first andsecond monolith are connected by the monolith bridge at the second endof the array.

16. Array according to any of points 9-15, wherein the monolith bridgeextends over less than 50%, preferably 40%, more preferably 30%, morepreferably 20%, and most preferably 10%, of the length from the first tothe second end of the first and second monoliths.

17. Array according to any of points 9-16, wherein said array has beenproduced by a process of comprising the steps of

A) providing the electrically conductive materials of the firstmonolith, the second monolith and the monolith bridge in the form ofthree separate entities, wherein the surface areas to be connected arein a moldable state,B) contacting the surface areas to be connected in the contact areas,C) joining the contact areas together by a method comprising a step ofsintering or oxidizing treatment.

When there are one or more intermediate monoliths and an end monolith inaddition to the first and second monoliths of the array, the array maystill be produced by the above process, wherein the three separateentities in these cases are any two of the juxtaposed monoliths and amonolith bridge in between them.

18. Array according to any of points 9-17, wherein said array has beenproduced by a process of comprising the steps of:

-   -   providing a first monolith component comprising metal powder        with a first alloy composition and a first soluble binder, the        first component having a first joining surface,    -   providing a second monolith component comprising metal powder        with a second alloy composition and a second soluble binder, the        second component having a second joining surface;    -   providing a bridge component comprising metal powder with a        third alloy composition and a third soluble binder, the bridge        component having two third joining surfaces, one at each end of        the bridge component;    -   wherein the first alloy composition and the second and third        alloy compositions all consist of a plurality of chemical        elements, and wherein the chemical elements are chosen so that,        for each of the chemical elements being present in an amount        higher than 0.5 weight % of the respective alloy composition,        that chemical element is comprised both in the first and second        and third alloy composition, and        -   for the chemical elements being present in the first alloy            composition in amounts of up to 5.0 weight %, the amount of            that chemical element differs by at most 1 percentage point            between the first alloy composition on the one hand and each            of the second and third alloy compositions on the other            hand, and        -   for the chemical elements being present in the first alloy            composition in amounts of more than 5.0 weight %, the amount            of that chemical element differs by at most 3 percentage            point between the first alloy composition on the one hand            and each of the second and third alloy compositions on the            other hand,    -   arranging the bridge component between the first monolith        component and the second monolith component so that one third        joining surface contacts the first joining surface and that the        other third joining surface contacts the second joining surface,    -   maintaining the joining surfaces in contact for a time period        allowing for at least some evaporation of the solvent; and    -   subsequently sintering or oxidizing the first, second and third        components together while maintaining the joining surfaces in        contact or as close together as possible in order to achieve the        array.

19. Array according to point 18, wherein the following step precedes thestep of arranging:

-   -   at least partly dissolving the first joining surface and/or the        second joining surface by applying a solvent.

20. Array according to any of points 12-19, wherein the conductivematerials of the monolith bridges are the same material.

21. Array according to any of points 12-19, wherein the conductivematerial of the monolith bridges at the second end of the array are thesame material.

22. Array according to any of points 9-21, wherein the conductivematerials of the monoliths and the monoliths bridges are the samematerial.

23. Array according to any points 9-22, wherein at least one of theelectrically conductive materials of the monoliths and of the at leastone monolith bridge is a composite of an electrically conductivemetallic material and a ceramic material.

24. Array according to any of items 9-23, wherein the resistivity of atleast one of the electrically conductive materials of the monoliths andthe monolith bridges is from 1×10E-4 Ohm×m to 1×10E-7 Ohm×m, preferablyfrom 1×10E-5 Ohm×m to 1×10E-7 Ohm×m, more preferably from 1×10E-5 Ohm×mto 5×10E-6 Ohm×m, and most preferably from 5×10E-5 Ohm×m to 1×10E-6Ohm×m.

25. Array according to any of points 9-24, wherein the monolith bridgematerial is heat-resistant up to a temperature of at least 500° C.,preferably at least 700° C., preferably at least 900° C., preferably atleast 1000° C., and most preferably at least 1100° C.

26. Array according to any of points 9-25, wherein the endothermicreaction is selected from the group consisting of steam methanereforming, hydrogen cyanide formation, methanol cracking, ammoniacracking, reverse water gas shift and dehydrogenation.

27. Array according to any of points 9-26, wherein the monoliths havesuch a shape that the cross section in a plane perpendicular to saidlongitudinal axis is selected form the group consisting of a polygon, aregular polygon, a circle, a semi-circle, an oval, a semi-oval, atrapeze, and wherein the monoliths may have the same or differentshapes.

28. Array according to point 27, wherein the monoliths have such a shapethat the cross section in a plane perpendicular to said longitudinalaxis is a regular polygon selected from a triangle, a rectangle, apentagon, a hexagon, a heptagon, an octagon, a nonagon, a decagon, ahendecagon and a dodecagon.

29. Array according to any of points 9-28, wherein the array furthercomprises an element for alleviating adverse effects caused by hot spotformation selected from the group consisting of:

-   -   (i) the two monoliths connected by the monolith bridge are        disposed so as to form a center plane positioned through the        geometric center of both of the two monoliths and positioned        parallel to the longitudinal axis of the array, wherein the        first and second monoliths have a first and a second width in        the direction perpendicular to said center plane, wherein said        monolith bridge has a width in the direction perpendicular to        said center plane, and wherein the width of the monolith bridge        is larger than said first and second widths,    -   (ii) the monolith bridge has a larger cross-sectional area at        one or both ends abutting the two monoliths to be connected than        at the center point of the bridge,    -   (iii) a safety bridge between monoliths, wherein the safety        bridge comprises a safety bridge electrically conductive        material having an electrical resistance, which is sufficient        high so as to restrain current from running through the safety        bridge when the monolith bridge is in operation, wherein the        safety bridge is positioned at any point between the first and        second end of the array;    -   (iv) a protrusion on at least one of the first and second        monolith for connecting the first and second conductor,        respectively, wherein the protrusion is of a protrusion        electrically conductive material;    -   (v) the monolith bridge material has a lower electrical        resistivity than the first electrically conductive material,    -   (vi) the monolith bridge comprises at least a first and a second        layer, wherein the first layer is positioned closer to the        second end of the array than the second layer, and wherein the        first layer has a lower electrical resistivity than the second        layer.

30. Array according to point 29 (i), the two monoliths to be connectedby the monolith bridge have a rectangular cross section in a planeperpendicular to said longitudinal axis and are arranged so as to haveparallel surfaces, wherein said two monoliths each have a front surfacefacing the other monolith, a back surface parallel to the front surfaceand two side surfaces perpendicular to the front and back surfaces,wherein the monolith bridge comprises one or more of (A) a spacersection positioned between at least part of the front surfaces, (B) oneor more side sections connected to at least part of one or more of theside surfaces, and (C) a back section connected to at least part of theback surface and connected to at least one side section.

31. Array according to point 30, wherein the bridge has a form selectedfrom the group consisting of an L-shaped body, an H-shaped body, aT-shaped body, an S-shaped body, an 8-shaped body, an O-shaped body, anF-formed body, an E-shaped body, and I-shaped body, two parallel linearbodies, and a rectangular frame body as viewed in the direction of thelongitudinal axis of the array, and wherein the bridge has a uniformdimension in the direction of the longitudinal axis of the array.

32. Array according to point 31, wherein each section of said bodies hasa rectangular cross section in a plane perpendicular to the surface ofthe monolith to which the section is connected.

33. Array according to point 30, wherein the side sections of the bridgeeach has a form of an elongated linear body with a longitudinal axisconnecting the side surfaces of the two monoliths to be connected andhaving a rectangular cross-section in a direction perpendicular to itslongitudinal direction.

34. Array according to point 32 or 33, wherein the side section extendsfrom the back surface of one monolith to the back surface of the secondmonolith.

35. Array according to any of points 32-34, wherein the elongated linearbody at the surface closest to the first end of the monolith hasextensions connected to the side surfaces of the monoliths.

36. Array according to point 35, wherein the extensions have the form ofa rectangular box as viewed in a direction perpendicular to the sidesurface.

37. Array according to point 36, wherein the extensions have the form ofa box with a triangular cross-section as viewed in a directionperpendicular to the side surface, wherein the triangle slopes from theback surface to the front surface.

38. Array according to point 30, wherein the side sections of the bridgeeach has the form of an elongated body with a longitudinal axisconnecting the side surfaces of the two monoliths to be connected andhaving a form as viewed from a direction perpendicular to the sidesurfaces with a straight line at the edge of the side section closest tothe second end of the monoliths and with a curve in the form of anpartial ellipse at the edge of the side section closest to the first endof the monoliths, wherein the curve in the form of an partial ellipsehas a declining profile in a direction from the back surfaces towardsthe front surfaces of the monoliths.

39. Array according to point 29 (vi), wherein the monolith bridgecontains one or more intermediate layers of an electrically conductivematerial positioned between the first and second layer, wherein theintermediate layers have such electrical resistivities that theresistivity is at increasing levels from layer to layer from the firstlayer to the secand layer.

40. Array according to point 29 (vi), wherein the first layer has alower resistivity than the resistivity of the first electricallyconductive material, and wherein the second layer has a higherresistivity than the first electrically conductive material.

41. Array according to any of points 9-40, wherein the array isconfigured to generate a heat flux of 500 to 50000 W/m² by resistanceheating of the material.

42. Array according to any of points 9-41, wherein the array haselectrically insulating parts arranged to increase the length of aprincipal current path between said at least two conductors to a lengthlarger than the largest dimension of the monolith.

43. Array according to any of points 9-42, wherein said array has atleast one electrically insulating part arranged to direct a currentthrough said monoliths in order to ensure that for at least 70% of thelength of said monoliths, a current density vector of the principalcurrent path has a non-zero component value parallel to the length ofsaid structured catalyst.

44. Array according to any of points 9-43, wherein the length of thefeed gas passage through the array is less than the length of thepassage of current from the first electrode through the array and to thesecond electrode.

45. Array according to any of points 9-44, wherein the monolith bridgematerial is a material devoid of any space with a smallest dimension of0.4 mm or more, preferably 0.6 mm or more, more preferably 0.8 mm ormore, more preferably 1.0 mm or more, more preferably 1.2 mm or more,more preferably 1.4 mm or more, more preferably 1.6 mm or more, morepreferably 1.8 mm or more, and most preferably 2.0 mm or more, formedtherein.

46. Array according to any of points 9-45, wherein the flow channels ofthe monoliths have such a shape that the cross section in a planeperpendicular to said longitudinal axis is selected from the groupconsisting of a polygon, a regular polygon, a circle, a semi-circle, anoval, a semi-oval, a trapeze, and wherein the flow channels may have thesame or different shapes within one monolith and/or between differentmonoliths.

47. Array according to point 46, wherein the flow channels of themonoliths have such a shape that the cross section in a planeperpendicular to said longitudinal axis is a regular polygon selectedfrom a triangle, a rectangle, a pentagon, a hexagon, a heptagon, anoctagon, a nonagon, a decagon, a hendecagon and a dodecagon.

48. A reactor system for carrying out an endothermic reaction of a feedgas, said reactor system comprising:

a) a catalyst of any of points 1-8, or the array of any of the points9-47;b) a pressure shell housing said array, said pressure shell comprisingan inlet for letting in said feed gas and an outlet for letting outproduct gas, wherein said inlet is positioned so that said feed gasenters said array in a first end and said product gas exits said arrayfrom a second; andc) a heat insulation layer between said structured catalyst and saidpressure shell.

49. Use of the catalyst according to any of points 1-8, or the array ofany of the points 9-47, or the reactor system of point 48, wherein theendothermic reaction is selected from the group consisting of steammethane reforming, hydrogen cyanide formation, methanol cracking,ammonia cracking, reverse water gas shift and dehydrogenation.

When a former point is referred back to, it also means referring back toany of the subpoints of the corresponding point.

SHORT DESCRIPTION OF THE FIGURES

FIG. 1 shows a perspective view of an array of the invention comprisingtwo monoliths and a monolith bridge.

FIG. 2 a perspective view of an array of the invention comprising fourmonoliths and three monolith bridges.

FIG. 3 shows a perspective view of an array of the invention comprisingtwo monoliths, a monolith bridge and a safety bridge.

FIG. 4 shows a perspective view of an array of the invention comprisingtwo monoliths and a monolith bridge with 3 layers.

FIG. 5 shows a perspective view of an array of the invention comprisingtwo monoliths and a monolith bridge in the form of an H.

FIG. 6 shows a perspective view of an array of the invention comprisingtwo monoliths and a monolith bridge in the form of an L.

FIG. 7 shows a perspective view of an array of the invention comprisingtwo monoliths and a monolith bridge in the form of an T.

FIG. 8 shows a perspective view of an array of the invention comprisingthree monoliths.

FIG. 9 shows a perspective view of an array of the invention comprisingfour monoliths and a monolith bridge at the second end of the array inthe form of a continuous layer surround three sides of all fourmonoliths.

FIG. 10 shows a perspective view of an array of the invention comprisingtwo monoliths and a monolith bridge at the second end of the array inthe form of two I-shaped boxes with triangular extensions.

FIG. 11 shows a perspective view of an array of the invention comprisingtwo monoliths and a monolith bridge at the second end of the array inthe form of two I-shaped boxes with cubic extensions.

FIG. 12 shows a perspective view of an array of the invention comprisingtwo monoliths and a monolith bridge at the second end of the array inthe form of two I-shaped bodies with a lower straight line edge and anupper edge with an outline as a partial ellipse.

FIG. 13 shows a perspective view of an array of the invention comprisingtwo monoliths and a monolith bridge at the second end of the array inthe form of an O-shaped box.

FIG. 14 shows a perspective view of an array of the invention comprisingtwo monoliths and a monolith bridge at the second end of the array inthe form of an 8-shaped box.

FIG. 15 shows pictures (FIGS. 15A, 15B and 15D) of an array according tothe invention and a chart (FIG. 15C) of material composition across thebridge.

FIG. 16 shows experimental data and operating temperature measuredduring a steam reforming experiment using an array of the invention.

FIG. 17 shows an example of the optimal geometry configuration ofmonoliths serially connected with monolith bridges in a structuredcatalyst for providing 500 kW of energy to facilitate an endothermicreaction at a roughly constant surface flux of 10 kW/m².

FIG. 18 shows experimental data for how the resistivity p of a materialvaries as a function of the content of ceramic in the form of AlO.

DETAILED DESCRIPTION OF THE FIGURES

FIG. 1 shows an array 10 of the invention with a first end 11 and asecond end 12 comprising a first monolith 13 and a second monolith 14and a monolith bridge 15 connecting the first and second monoliths 13and 14. The first and second monoliths 13 and 14 are in the form of astructured catalyst comprising a macroscopic structure of anelectrically conductive material, said macroscopic structure supportinga ceramic coating, wherein said ceramic coating supports a catalyticallyactive material. The monolith bridge is made of an electricallyconductive material.

The first and second monoliths 13 and 14 are connected to a first andsecond conductor (not shown) connected to an external electrical powersupply (not shown). The first and second monoliths 13 and 14 and themonolith bridge 15 enable heating thereof when connected to the externalelectrical power supply.

The first and second monoliths 13 and 14 have flow channels formedtherein extending from the first end 11 to the second end 12 of thearray 10 and adapted for leading a feed gas through the array 10 fromthe first end 11 to the second end 12 to heat the feed gas whileexposing it to the catalyst. The monolith bridge 15 is devoid of anyflow channels, i.e. it is constituted by a material with a continuousstructure.

FIG. 2 shows an array 20 of the invention with a first end 21 and asecond end 22 comprising a first monolith 23, a second monolith 24, anintermediate monolith 25, an end monolith 26, a monolith bridge 27 atthe second end 22 of the array between the first and second monoliths 23and 24, a monolith bridge 28 at the first end 21 of the array betweenthe second monolith 24 and the intermediate monolith 25 and a monolithbridge 29 at the second end 22 of the array between the intermediatemonolith 25 and the end monolith 26. The monoliths 23, 24, 25 and 26have flow channels 30 formed therein extending from the first end 21 tothe second end 22 of the array 20 and adapted for leading a feed gasthrough the array 20 from the first end 21 to the second end 22. Themonolith bridges 27, 28 and 29 are devoid of any flow channels, i.e. itis constituted by material with a uniform structure.

FIG. 3 shows an array 40 of the invention with a first end 41 and asecond end 42 comprising a first monolith 43 and a second monolith 44and monolith bridge 45 connecting the first and second monoliths 43 and44. The first and second monoliths 43 and 44 have flow channels 46formed therein extending from the first end 41 to the second end 42 ofthe array 40 and adapted for leading a feed gas through the array 40from the first end 41 to the second end 42. The monolith bridge 45 isdevoid of any flow channels, i.e. it is constituted by a material with auniform structure.

The array 40 also comprises a safety bridge 47 of a conductive materialwith a resistivity, which is sufficiently high to prevent or stronglyreduce passing of current therethrough when the monolith bridge 45 isoperational for passing of current therethrough. However, in case themonolith bridge 45 becomes non-operational, e.g. due to damage, currentwill pass through the safety bridge 47 to ensure continued operation ofthe array.

FIG. 4 shows an array 50 of the invention with a first end 51 and asecond end 52 comprising a first monolith 53 and a second monolith 54and monolith bridge 55 connecting the first and second monoliths 53 and54. The first and second monoliths 53 and 54 have flow channels formedtherein extending from the first end 51 to the second end 52 of thearray 50 and adapted for leading a feed gas through the array 50 fromthe first end 51 to the second end 52. The monolith bridge 55 is devoidof any flow channels, i.e. it is constituted by a material with uniformstructure.

The monolith bridge 55 is composed of three layers of an electricallyconductive material comprising a first layer 56, an intermediate layer57 and a second layer 58. The conductivity of the first layer 56 ishigher than the conductivity of the first and second monoliths 53 and54. The conductivity of the intermediate layer 57 is lower than theconductivity of the first and second monoliths 53 and 54. Theconductivity of the second layer 58 is lower than the conductivity ofthe intermediate layer 57. The level of conductivity in the three layers56, 57 and 58 are selected so that the current passing from the first tothe second monolith is approximately evenly distributed between thethree layers.

To help further obtain such evenly distribution of current between thethree layers 56, 57 and 58, the thickness of layer 56 is higher thanthat of layer 57, and the thickness of layer 57 is higher than that oflayer 58.

This configuration of the monolith bridge ensures a relative low currentdensity in the monolith bridge and thereby reduces the risk of hotspots.

FIG. 5 shows an array 60 of the invention with a first end 61 and asecond end 62 comprising a first monolith 63 and a second monolith 64and monolith bridge 65 connecting the first and second monoliths 63 and64. The first and second monoliths 63 and 64 have flow channels 66formed therein extending from the first end 61 to the second end 62 ofthe array 60 and adapted for leading a feed gas through the array 60from the first end 61 to the second end 62. The monolith bridge 65 isdevoid of any flow channels, i.e. it is constituted by a material withuniform structure.

The first and second monoliths 63 and 64 have a quadratic cross sectionand are arranged so as to have parallel surfaces. The monolith bridge 65is composed of a bridge in the form of a H-shaped box comprising aspacer section 67 with a quadratic cross section disposed between thetwo front surfaces 68 and 69 of the first and second monoliths 63 and 64facing each other and two linear sections 70 and 71 with a quadraticcross section, wherein section 70 is connected to the side surfaces 72and 73 of one side of the monoliths 63 and 64 and to the side surfacesof the spacer section 67, and wherein section 71 is connected to theside surfaces 74 and 75 of the opposite side of the monoliths 63 and 64and to the side surfaces of the spacer section 67.

The electrical current running from the first monolith 63 to the secondmonolith 64 will run partly through the spacer section 67 and partlythrough the linear sections 70 and 71. Thus, the H-shaped bridgeprovides an increased cross section for the current to run through andhence a reduced current density and a reduced heating of the bridge,which in turn reduces the risk of hot spots from occurring.

FIG. 6 shows an array 80 comprising a first monolith 81 and a secondmonolith 82 and a monolith bridge 83 connecting the first and secondmonoliths 81 and 82. The first and second monoliths 81 and 82 have aquadratic cross section and are arranged so as to have parallelsurfaces. The monolith bridge 83 is composed of a bridge in the form ofan L-shaped box comprising a spacer section 84 with a quadratic crosssection disposed between the two front surfaces 85 and 86 of the firstand second monoliths 81 and 82 facing each other and one linear section87 with a quadratic cross section, wherein section 87 is connected tothe side surface 88 on one side of the monolith 82 and to a side surfaceof the spacer section 84.

The electrical current running from the first monolith 81 will runpartly through the spacer section 84 directly into the second monolith82 and partly through the spacer section 84 into the linear section 87and then into the second monolith 82. Thus, the L-shaped bridge providesan increased cross section for the current to run through and hence areduced current density and a reduced heating of the bridge, which inturn reduces the risk of hot spots from occurring.

FIG. 7 shows an array 90 comprising a first monolith 91 and a secondmonolith 92 and a monolith bridge 93 connecting the first and secondmonoliths 91 and 92. The first and second monoliths 91 and 92 have aquadratic cross section and are arranged so as to have parallelsurfaces. The monolith bridge 93 is composed of a bridge in the form ofa T-shaped box comprising a spacer section 94 with a quadratic crosssection disposed between the two front surfaces 95 and 96 of the firstand second monoliths 91 and 92 facing each other and one linear section97 with a quadratic cross section, wherein section 97 is connected tothe two side surfaces 98 and 99 on one side of the monoliths 91 and 92and to a side surface of the spacer section 94.

The electrical current running from the first monolith 91 to the secondmonolith 92 will run partly through the spacer section 94 and partlythrough the linear section 97. Thus, the T-shaped bridge provides anincreased cross section for the current to run through and hence areduced current density and a reduced heating of the bridge, which inturn reduces the risk of hot spots from occurring.

FIG. 8 shows an array 110 with a first end 111 and a second end 112comprising a first monolith 113, a second monolith 114 and an endmonolith 115. The first monolith 113 is connected to the second monolith114 with a monolith bridge 116 at the second end of the array. Thesecond monolith 114 is connected to the end monolith 115 with a monolithbridge 117 at the first end of the array. A first conductor 118 isconnected to the first end 111 of the first monolith 113 and a secondconductor 119 is connected to the first end 111 of the end monolith 115.In this embodiment, the end monolith will be heated by the gas passingthrough it.

FIG. 9 shows an array 120 with a first end 121 and a second end 122comprising two first monoliths 123 and 124 and two end monoliths 125 and126. All four monoliths are connected at the second end by a monolithbridge 127 in the form of a layer surrounding three sides of all fourmonoliths. First conductors 128 and 129 are connected to the first end121 of the first monoliths 123 and 124 and second conductors 130 and 131are connected to the first end 121 of the end monoliths 125 and 126.

By means of conductor 128 electrical current is lead to the firstmonoliths 123 and through the bridge 127 to end monoliths 125 and 126.Likewise, by means of conductor 129 electrical current is lead to thefirst monoliths 124 and through the bridge 127 to end monoliths 125 and126. Such a construction may be referred to as a parallel coupling. Thearray 120 has the advantage that in case one of the units consisting ofconductor and monolith becomes defective during use hence preventingcurrent from running therethrough, the array will continue to befunctional and the operation of the reactor using the array for carryingout an endothermic reaction will not be interrupted. Also, the parallelcoupling of array 120 is advantageous in that it is capable of handling3 phase energy supply.

FIG. 10 shows an array 140 comprising a first monolith 141 and a secondmonolith 142 and a monolith bridge 143 connecting the first and secondmonoliths 141 and 142. The first and second monoliths 141 and 142 have aquadratic cross section and are arranged so as to have parallelsurfaces. The monolith bridge 143 is in the form of two box-shapedlinear sections 144 and 145 with a quadratic cross section, whereinsection 144 on one side of the monoliths 141 and 142 is connected to thetwo side surfaces 146 and 147 of the monoliths 141 and 142, and whereinsection 145 on the opposing side of the monoliths 141 and 142 isconnected to the two side surfaces 148 and 149 of the monoliths 141 and142.

The linear section 144 comprise extensions 150 and 151 at the endsituated closest to the first end of the array 140. The linear section145 comprise extensions 152 and 153 at the end situated closest to thefirst end of the array 140. The extensions 150-153 have the form of abox with a triangular cross-section as viewed in a directionperpendicular to the side surface, wherein the triangle slopes from theback surface of the monoliths 141 and 142 to their front surface.

The electrical current running from the first monolith 141 to the secondmonolith 142 will run partly through the linear sections 144 and 145 andpartly through the triangular extensions. Thus, the bridge 143 providesan increased cross section area for the current to run through and hencea reduced resistivity and a reduced heating of the bridge, which in turnreduces the risk of hot spots from occurring. Moreover, due to fact thatthe cross-sectional area of the extensions 150-153 increases towards theback surface of the monoliths, the flow of current is distributed overthe full extension of the side surfaces of the monoliths. Thus, by sucha design the risk of hot spots occurring is even further reduced.

FIG. 11 shows an array 160 comprising a first monolith 161 and a secondmonolith 162 and a monolith bridge 163 connecting the first and secondmonoliths 161 and 162. The first and second monoliths 161 and 162 have aquadratic cross section and are arranged so as to have parallelsurfaces. The monolith bridge 163 is in the form of two box-shapedlinear sections 164 and 165 with a quadratic cross section, whereinsection 164 on one side of the monoliths 161 and 162 is connected to thetwo side surfaces 166 and 167 of the monoliths 161 and 162, and whereinsection 165 on the opposing side of the monoliths 161 and 162 isconnected to the two side surfaces 168 and 169 of the monoliths 161 and162.

The linear section 164 comprise extensions 170 and 171 at their endsituated closest to the first end of the array 160. The linear section165 comprise extensions 172 and 173 at their end situated closest to thefirst end of the array 160. The extensions 170-173 have the form of abox with a quadratic cross-section as viewed in a directionperpendicular to the side surface.

The design of the bridge 163 reduces the risk of hot spots fromoccurring for the same reasons as described in connection with FIG. 10 .

FIG. 12 shows an array 180 comprising a first monolith 181 and a secondmonolith 182 and a monolith bridge connecting the first and secondmonoliths 181 and 182. The first and second monoliths 181 and 182 have aquadratic cross section and are arranged so as to have parallelsurfaces. The monolith bridge comprises a spacer section 183 with arectangular cross section disposed between the two front surfaces 184and 185 of the first and second monoliths 181 and 182 and two elongatedside sections 186 and 187 with a quadratic cross section, whereinsection 186 is connected to the side surfaces 188 and 189 of one side ofthe monoliths 181 and 182 but not to the side surface of the spacersection 183, and wherein section 187 is connected to the side surfaces190 and 191 of the opposite side of the monoliths 181 and 182 but not tothe side surface of the spacer section 183.

The side sections 186 and 187 each has the form of an elongated bodywith a longitudinal axis connecting the side surfaces of the twomonoliths to be connected and having a form as viewed from a directionperpendicular to the side surfaces with a straight line at the edge ofthe side section closest to the second end of the monoliths and with acurve in the form of an partial ellipse at the edge of the side sectionclosest to the first end of the monoliths, wherein the curve in the formof an partial ellipse has a declining profile in a direction from theback surfaces towards the front surfaces of the monoliths. Such a designallows for a better current distribution, and thereby reduced risk ofhot spot development.

FIG. 13 shows an array 200 comprising a first monolith 201 and a secondmonolith 202 and a monolith bridge 203 connecting the first and secondmonoliths 201 and 202. The first and second monoliths 201 and 202 have aquadratic cross section and are arranged so as to have parallelsurfaces. The monolith bridge 203 has the form of a box-shaped,rectangular frame with a rectangular cross section, wherein said frameis connected to the side surfaces and the back surface of the monoliths201 and 202. Such a design allows for a better current distribution, andthereby reduced risk of hot spot development.

FIG. 14 shows an array 210 with the same construction as that of thearray shown in FIG. 13 except that the monolith bridge in addition tothe box-shaped, rectangular frame 211 comprises a spacer section 212disposed between the two front surfaces 213 and 214 of the first andsecond monoliths 215 and 216. The side surfaces of the spacer section212 are connected to the side surfaces of the said frame. Such a designallows for even better current distribution, and thereby reduced risk ofhot spot development.

EXAMPLES Example 1: Photographic Analysis of Array of the Invention andTesting of Structural Properties

FIG. 15 shows an example of an array according to the invention, wheretwo monoliths of 10 channels are connected with a monolith bridge. Themonolith has a length of 12 cm and a rectangular cross-sectional planewith dimensions 1.5×3.0 cm. The monolith bridge has a length of 1.3 cmbetween the monoliths and is connected to the monoliths with a contactarea of 1.0×3.0 cm.

All three entities were prepared from the same metal powder material ofFeCrAlloy. Analyzing the bridge with scanning electron microscopy andenergy-dispersive X-ray spectroscopy shows:

-   -   1. Visually the bridge cannot be distinguished from the        monoliths as there is no apparent separation or interface        between the connected sections in the SEM pictures, cf. FIGS.        15A, 15B and 15D. The only distinguishing feature between the        three entities is a slightly higher porosity in the monoliths as        compared to the bridge material, resulting in a higher        proportion of voids in the monoliths.    -   2. The material composition across the monolith-bridge-monolith        section is indistinguishable, cf. FIG. 15C, because the same        metal powder material was used as illustrated by the line scan        analysis. Also, the graph confirms that there is no apparent        difference in material composition in the interface between the        connected sections as compared to the composition in the        monoliths and bridge. The drops in signal of the graph of FIG.        15C is a consequence of scanning through a void in the material.

Example 2: Experimental Data and Operating Temperature Measured During aSteam Reforming Experiment Using an Array of the Invention

FIG. 16 shows experimental data and operating temperature measuredduring a steam reforming reaction experiment in an array according tothe invention, where 4 monoliths with an outer dimension of 12 cm(length)×1 cm×1 cm are connected with monolith bridges with a length of1.3 mm between the monoliths at alternating ends. An AC-power supply isconnected to the uppermost 1 cm of the first end of the first monolithand the uppermost 1 cm of the first end of the fourth monolith. In theexperiment, a feedstock of 32% CH₄, 2% H₂, and 66% H₂O with a total feedflow of 100 Nl/h was fed to a reactor system of the invention at a feedtemperature of 251° C. and a pressure of 9 barg, where the feedtemperature corresponds to the temperature of the first end of thearray. The data shows the temperature measured close to the second endof the monoliths as a function of the energy flux into the feed gas.This illustrates how this embodiment of the array of the invention istemperature resistant to at least 1180° C. in the experiment withoutexperiencing any mechanical failure. Additionally, the data illustratesthat the invention allows for having an electrically heated array with apronounced temperature profile over the length of the array, where inthe given case the temperature increases approximately 900° C. from thefirst to the second end. It is an advantage of the invention to have arelatively colder end to handle the electrical connections withelectrical conductors to the attached power supply, while still reachinghigh outlet temperatures to facilitate high temperature endothermicreactions.

Example 3: Optimal Geometry Configuration of Monoliths SeriallyConnected with Monolith Bridges

FIG. 17 shows an example of an optimal geometry configuration ofmonoliths serially connected with monolith bridges in an array of theinvention for providing 500 kW of energy to facilitate an endothermicreaction at a roughly constant surface flux of 10 kW/m² using anelectrical circuit of 800 A and 625 V. The monoliths have squarechannels of approximately 0.25 cm×0.25 cm, walls with a thickness of0.44 mm, and a length of 0.5 m. The example illustrates the requiredcross section of the monolith as a function of the practical resistance.A number of arrays are tested, which have different resistivitiesachieved by using different material compositions in the form of acomposite of a metallic material and a ceramic material.

The experiment illustrates that by applying a higher resistance monolithas achieved by the composite material, an increased cross section of themonolith can be used which provides a possibility of reducing the numberof monoliths required. This in turn reduces the required number ofmonolith bridges and hence the number of connection required toconstruct an array of the invention. Overall, the graph illustrates howthe concept of the present invention with respect to connectingmonoliths and with respect to selecting materials with differentresistivities collectively enables production of a monolith array withimproved properties.

Example 4

FIG. 18 shows results obtained during the development of the presentinvention. It shows how the resistivity p of a material varies as afunction of the content of ceramic in the form of AlO. The graph isbased on experiments where the resistivity along a composite componentas used in the catalyst of the invention as described above wasmeasured. The resistivity was measured by applying a known current tothe component and measuring the voltage drop with two probes arranged incontact with the component with a fixed distance between them. Theexperiments were made both at room temperature and at a highertemperature, and both showed varying resistivity.

The experiments show that it is possible to produce a composite materialof an electrically conductive metallic material and a ceramic materialwith a selected resistivity within wide ranges.

1. A structured catalyst arranged for catalyzing an endothermic reactionof a feed gas, said structured catalyst comprising a macroscopicstructure of electrically conductive material, said macroscopicstructure supporting a ceramic coating, wherein said ceramic coatingsupports a catalytically active material, wherein the electricallyconductive material is a composite in the form of a homogenous mixtureof an electrically conductive metallic material and a ceramic material.2. Catalyst according to claim 1, wherein the metallic material is analloy comprising one or more substances selected from the groupconsisting of Fe, Cr, Al, Co, Ni, Zr, Cu, Ti, Mn, and Si.
 3. Catalystaccording to claim 1, wherein the ceramic material is an oxide of asubstance selected from the group consisting of Al, Mg, Ce, Zr, Ca, Yand La.
 4. Catalyst according to claim 1, wherein the ratio based onweight of metallic material to ceramic material in the macroscopicstructure is in the range of from 50 to
 1. 5. Catalyst according toclaim 1, wherein the structured catalyst has the form of at least onemonolith, wherein the monolith has a number of flow channels formedtherein for conveying said feed gas through the monoliths from a firstend, where the feed gas enters, to a second end, where a product gasexits, wherein said monolith has a longitudinal axis extending form saidfirst end to said second end.
 6. Catalyst according to claim 5, whereinthe macroscopic structure of the monolith is composed of two or morecomposite materials with different compositions positioned in thedirection of said longitudinal axis so as provide differentresistivities.
 7. Catalyst according to claim 6, wherein the macroscopicstructure of the monolith is composed of at least three compositematerials.
 8. Catalyst according to claim 7, wherein the macroscopicstructure of the monolith comprises at least a first, a second and athird composite material positioned in the direction from the first tothe second end, wherein the second composite material has a higherresistivity as compared to the first and third composite material, thethird composite material has a lower resistivity as compared to thefirst and second composite material, and the first composite materialhas a resistivity in between the second and third composite material. 9.Array comprising a first and a second structured catalyst according toclaim 1, wherein: a) the first and second structured catalyst have theform of a first and second monolith respectively, b) each of said firstand second monoliths has a number of flow channels formed therein forconveying said feed gas through the monoliths from a first end, wherethe feed gas enters, to a second end, where a product gas exits, whereineach of said first and second monoliths has a longitudinal axisextending from said first end to said second end; c) the array comprisesat least a first and a second conductor electrically connected to saidfirst and second monoliths, respectively, and configured to be connectedto an electrical power supply, wherein said electrical power supply isdimensioned to heat at least part of said first and second monoliths toa temperature of at least 500° C. by passing an electrical currentthrough said macroscopic structure, wherein said first conductor iselectrically connected directly or indirectly to the first monolith andthe second conductor is electrically connected directly or indirectly tothe second monolith, and wherein the conductors are connected atpositions on the array closer to said first end than to said second end,d) said first and second monolith are electrically connected by amonolith bridge of a monolith bridge electrically conductive material,e) the array is configured to direct an electrical current to run fromthe first conductor through the first monolith to said second end, thenthrough the bridge, and then through the second monolith to the secondconductor, and f) said array has been produced by a process comprisingthe steps of i) providing the electrically conductive materials of thefirst monolith, the second monolith and the monolith bridge in the formof three separate entities, and ii) joining the separate entitiestogether by a method comprising a step of sintering or oxidizingtreatment.
 10. Array according to claim 9, wherein the second conductoris indirectly electrically connected to the second monolith.
 11. Arrayaccording to claim 10, wherein the array further comprises (i) one ormore juxtaposed additional intermediate monoliths of a structuredcatalyst and (ii) one end monolith of a structured catalyst, whereineach additional intermediate monolith is connected to at least twojuxtaposed monoliths by a monolith bridge of a monolith bridgeelectrically conductive material, and wherein the end monolith isconnected to at least one juxtaposed monolith, and wherein the secondconductor is connected to the end monolith at a position on the monolithcloser to said first end than to said second end.
 12. Array according toclaim 9, wherein the said first and second monolith are connected by themonolith bridge at the second end of the array.
 13. Array according toclaim 9, wherein said array has been produced by a process of comprisingthe steps of A) providing the electrically conductive materials of thefirst monolith, the second monolith and the monolith bridge in the formof three separate entities, wherein the surface areas to be connectedare in a moldable state, B) contacting the surface areas to be connectedin the contact areas, C) joining the contact areas together by a methodcomprising a step of sintering or oxidizing treatment.
 14. Arrayaccording to claim 9, wherein said array has been produced by a processof comprising the steps of: providing a first monolith componentcomprising metal powder with a first alloy composition and a firstsoluble binder, the first component having a first joining surface,providing a second monolith component comprising metal powder with asecond alloy composition and a second soluble binder, the secondcomponent having a second joining surface; providing a bridge componentcomprising metal powder with a third alloy composition and a thirdsoluble binder, the bridge component having two third joining surfaces,one at each end of the bridge component; wherein the first alloycomposition and the second and third alloy compositions all consist of aplurality of chemical elements, and wherein the chemical elements arechosen so that, for each of the chemical elements being present in anamount higher than 0.5 weight % of the respective alloy composition,that chemical element is comprised both in the first and second andthird alloy composition, and for the chemical elements being present inthe first alloy composition in amounts of up to 5.0 weight %, the amountof that chemical element differs by at most 1 percentage point betweenthe first alloy composition on the one hand and each of the second andthird alloy compositions on the other hand, and for the chemicalelements being present in the first alloy composition in amounts of morethan 5.0 weight %, the amount of that chemical element differs by atmost 3 percentage point between the first alloy composition on the onehand and each of the second and third alloy compositions on the otherhand, arranging the bridge component between the first monolithcomponent and the second monolith component so that one third joiningsurface contacts the first joining surface and that the other thirdjoining surface contacts the second joining surface, maintaining thejoining surfaces in contact for a time period allowing for at least someevaporation of the solvent; and subsequently sintering or oxidizing thefirst, second and third components together while maintaining thejoining surfaces in contact or as close together as possible in order toachieve the array.
 15. Array according to claim 14, wherein thefollowing step precedes the step of arranging: at least partlydissolving the first joining surface and/or the second joining surfaceby applying a solvent.
 16. A reactor system for carrying out anendothermic reaction of a feed gas, said reactor system comprising: a) acatalyst of claim 1; b) a pressure shell housing said catalyst, saidpressure shell comprising an inlet for letting in said feed gas and anoutlet for letting out product gas, wherein said inlet is positioned sothat said feed gas enters said catalyst in a first end and said productgas exits said catalyst from a second end; and c) a heat insulationlayer between said structured catalyst and said pressure shell. 17.(canceled)
 18. A structured catalyst arranged for catalyzing anendothermic reaction of a feed gas, said structured catalyst comprisinga macroscopic structure of electrically conductive material, saidmacroscopic structure supporting a ceramic coating, wherein said ceramiccoating supports a catalytically active material, wherein theelectrically conductive material at least partly is a composite in theform of a homogenous mixture of an electrically conductive metallicmaterial and a ceramic material, wherein the macroscopic structure atleast partly is composed of two or more materials with differentresistivities.
 19. Catalyst according to claim 18, wherein themacroscopic structure at least partly is composed of one or morecomposite materials and one or more non-composite electricallyconductive metallic materials.
 20. Catalyst according to claim 18,wherein the metallic material is an alloy comprising one or moresubstances selected from the group consisting of Fe, Cr, Al, Co, Ni, Zr,Cu, Ti, Mn, and Si.
 21. Catalyst according to claim 18, wherein theceramic material is an oxide of a substance selected from the groupconsisting of Al, Mg, Ce, Zr, Ca, Y and La.
 22. Catalyst according toclaim 18, wherein the ratio based on weight of metallic material toceramic material in the macroscopic structure is in the range of from 50to
 1. 23. Catalyst according to claim 18, wherein the structuredcatalyst has the form of at least one monolith, wherein the monolith hasa number of flow channels formed therein for conveying said feed gasthrough the monoliths from a first end, where the feed gas enters, to asecond end, where a product gas exits, wherein said monolith has alongitudinal axis extending form said first end to said second end. 24.Catalyst according to claim 23, wherein the macroscopic structure of themonolith is composed of two or more composite materials with differentcompositions positioned in the direction of said longitudinal axis so asprovide different resistivities.
 25. Catalyst according to claim 24,wherein the macroscopic structure of the monolith is composed of atleast three composite materials.
 26. Catalyst according to claim 25,wherein the macroscopic structure of the monolith comprises at least afirst, a second and a third composite material positioned in thedirection from the first to the second end, wherein the second compositematerial has a higher resistivity as compared to the first and thirdcomposite material, the third composite material has a lower resistivityas compared to the first and second composite material, and the firstcomposite material has a resistivity in between the resistivity of thesecond and third composite material.
 27. Catalyst according to claim 23,wherein the macroscopic structure of the monolith is composed of one ormore composite materials with different compositions and onenon-composite electrically conductive metallic material positioned inthe direction of said longitudinal axis so as provide differentresistivities.
 28. Catalyst according to claim 27, wherein themacroscopic structure of the monolith comprises at least a first and asecond composite material and a non-composite electrically conductivemetallic material positioned in the direction from the first to thesecond end, wherein the second composite material has a higherresistivity as compared to the first composite material and thenon-composite material, the non-composite material has a lowerresistivity as compared to the first and second composite material, andthe first composite material has a resistivity in between theresistivity of the second composite material and the resistivity of thenon-composite material.
 29. Array comprising a first and a secondstructured catalyst according to claim 18, wherein: a) the first andsecond structured catalyst have the form of a first and a secondmonolith, respectively; b) each of said first and second monoliths has anumber of flow channels formed therein for conveying said feed gasthrough the monoliths from a first end, where the feed gas enters, to asecond end, where a product gas exits, wherein each of said first andsecond monoliths has a longitudinal axis extending from said first endto said second end; c) the array comprises at least a first and a secondconductor electrically connected to said first and second monoliths,respectively, and configured to be connected to an electrical powersupply, wherein said electrical power supply is dimensioned to heat atleast part of said first and second monoliths to a temperature of atleast 500° C. by passing an electrical current through said macroscopicstructure, wherein said first conductor is electrically connecteddirectly or indirectly to the first monolith and the second conductor iselectrically connected directly or indirectly to the second monolith,and wherein the conductors are connected at positions on the arraycloser to said first end than to said second end, d) said first andsecond monolith are electrically connected by a monolith bridge of amonolith bridge electrically conductive material, e) the array isconfigured to direct an electrical current to run from the firstconductor through the first monolith to said second end, then throughthe bridge, and then through the second monolith to the secondconductor, and f) said array has been produced by a process comprisingthe steps of i) providing the electrically conductive materials of thefirst monolith, the second monolith and the monolith bridge in the formof three separate entities, and ii) joining the separate entitiestogether by a method comprising a step of sintering or oxidizingtreatment.
 30. Array according to claim 29, wherein the second conductoris indirectly electrically connected to the second monolith.
 31. Arrayaccording to claim 30, wherein the array further comprises (i) one ormore juxtaposed additional intermediate monoliths of a structuredcatalyst and (ii) one end monolith of a structured catalyst, whereineach additional intermediate monolith is connected to at least twojuxtaposed monoliths by a monolith bridge of a monolith bridgeelectrically conductive material, and wherein the end monolith isconnected to at least one juxtaposed monolith, and wherein the secondconductor is connected to the end monolith at a position on the monolithcloser to said first end than to said second end.
 32. Array according toclaim 29, wherein the said first and second monolith are connected bythe monolith bridge at the second end of the array.
 33. Array accordingto claim 29, wherein said array has been produced by a process ofcomprising the steps of A) providing the electrically conductivematerials of the first monolith, the second monolith or the intermediatemonoliths and the monolith bridge in the form of three separateentities, wherein the surface areas to be connected are in a moldablestate, B) contacting the surface areas to be connected in the contactareas, C) joining the contact areas together by a method comprising astep of sintering or oxidizing treatment.
 34. Array according to claim29, wherein said array has been produced by a process of comprising thesteps of: providing a first monolith component comprising metal powderwith a first alloy composition and a first soluble binder, the firstcomponent having a first joining surface, providing a second monolithcomponent comprising metal powder with a second alloy composition and asecond soluble binder, the second component having a second joiningsurface; providing a bridge component comprising metal powder with athird alloy composition and a third soluble binder, the bridge componenthaving two third joining surfaces, one at each end of the bridgecomponent; wherein the first alloy composition and the second and thirdalloy compositions all consist of a plurality of chemical elements, andwherein the chemical elements are chosen so that, for each of thechemical elements being present in an amount higher than 0.5 weight % ofthe respective alloy composition, that chemical element is comprisedboth in the first and second and third alloy composition, and for thechemical elements being present in the first alloy composition inamounts of up to 5.0 weight %, the amount of that chemical elementdiffers by at most 1 percentage point between the first alloycomposition on the one hand and each of the second and third alloycompositions on the other hand, and for the chemical elements beingpresent in the first alloy composition in amounts of more than 5.0weight %, the amount of that chemical element differs by at most 3percentage point between the first alloy composition on the one hand andeach of the second and third alloy compositions on the other hand,arranging the bridge component between the first monolith component andthe second monolith component so that one third joining surface contactsthe first joining surface and that the other third joining surfacecontacts the second joining surface, maintaining the joining surfaces incontact for a time period allowing for at least some evaporation of thesolvent; and subsequently sintering or oxidizing the first, second andthird components together while maintaining the joining surfaces incontact or as close together as possible in order to achieve the array.35. Array according to claim 34, wherein the following step precedes thestep of arranging: at least partly dissolving the first joining surfaceand/or the second joining surface by applying a solvent.
 36. A reactorsystem for carrying out an endothermic reaction of a feed gas, saidreactor system comprising: a) a catalyst of claim 18; b) a pressureshell housing said catalyst, said pressure shell comprising an inlet forletting in said feed gas and an outlet for letting out product gas,wherein said inlet is positioned so that said feed gas enters saidcatalyst in a first end and said product gas exits said catalyst from asecond end; and c) a heat insulation layer between said structuredcatalyst and said pressure shell.
 37. (canceled)